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Creamy Dairy-Free Broccoli and Cauliflower Casserole

Creamy Dairy-Free Broccoli and Cauliflower Casserole with caramelized onion topping is rich in flavor, has the most delightful creamy texture, and tastes like it’s loaded with yummy cheese! You’d never guess this delicious healthy broccoli and cauliflower casserole contains zero dairy.

Full casserole dish of broccoli cauliflower casserole with caramelized onions on top.

Several years ago, I posted a Creamy Cauliflower Casserole recipe that was a huge hit. While it’s still both a reader and a family favorite, I wanted to create a recipe that was entirely dairy-free for anyone to enjoy.

But don’t worry…it may be dairy-free, but it still tastes like the real deal!

I designed the sauce to have a creamy, cheesy flavor without the need for cream, cream cheese, sour cream, or grated cheese. 

I’m willing to bet your friends and family will think it tastes just like a regular cheesy broccoli cauliflower casserole! How bad could that be, right?

The caramelized onions add a marvelous rich depth of flavor reminiscent of melted butter that makes this easy side dish taste bold and delicious.

Be sure to give the onions plenty of time to caramelize for the absolute perfect side dish!

Vertical image of wooden spoon taking a scoop of broccoli casserole.

Let’s discuss the simple ingredients needed to make this Broccoli Cauliflower Casserole!

Ingredients for Dairy-Free Broccoli Cauliflower Casserole:

Broccoli: One large fresh broccoli crown makes up the broccoli portion of the recipe. While you can purchase a full stalk of broccoli, I tend to use mostly just the florets. If you enjoy the stems, feel free to get a full stalk and toss in the chopped stem too!

Cauliflower: The other star ingredient here! A fresh head of cauliflower gets chopped into florets for this healthy casserole recipe.

Full-Fat Canned Coconut Milk: The majority of the sauce for this simple casserole is full-fat canned coconut milk. While that may seem odd if you aren’t experienced using it, trust me: it works wonders as a replacement for heavy cream in almost any recipe, sweet or savory!

I’m willing to bet if you don’t tell someone the sauce is made with it, they won’t notice any coconut flavor at all.

Cider Vinegar: The combination of apple cider vinegar and coconut milk is what gives the sauce that rich tangy flavor, similar to a creamy cheese sauce. 

Fresh Garlic: Garlic cloves bring a big bold flavor to the sauce, also contributing to the cheesy vibe since cheese and garlic are often paired together.

Egg Yolks: A couple egg yolks are added to the creamy sauce to bring thickness and rich flavor. Skip the egg yolks if you’re vegan or have an egg allergy. They do make the sauce richer but it will still be delicious without them.

Gluten-Free All-Purpose Flour: A couple tablespoons of a gluten-free flour blend is added to the sauce to help thicken it up. I use Bob’s Red Mill Gluten-Free 1-to-1 Baking Flour, but you can also use King Arthur or Pamela’s. You can also use regular all-purpose flour if you aren’t gluten-free.

Avocado Oil: A little avocado oil or extra virgin olive oil is used to coat the cauliflower and broccoli for roasting, and it is also used to caramelize the onions for the topping. I prefer using avocado oil because it is ideal for cooking at high temperatures and it has a neutral flavor.

Onions: Two large yellow onions are thinly sliced and cooked slowly in a skillet until they are richly golden brown and caramelized. This process gives the onions deep, buttery flavor and makes them taste positively exquisite! They add a fancy vibe to the casserole.

Almond Flour: To bring a little texture to the otherwise soft caramelized onions, we toss in some almond flour. If you don’t have almond flour on hand, replace it with bread crumbs or cassava flour.

Sea Salt: Add kosher salt to your personal taste! If you feel the casserole tastes at all bland, continue adding sea salt a little at a time until it tastes nice and creamy and cheesy. Add in black pepper to taste if you like it too.

Fresh out of the oven Broccoli Cauliflower Casserole with a golden napkin to the side.

Optional Additions:

  • If you don’t need this casserole to be entirely dairy-free, add 1 to 2 cups of grated colby jack cheese, gruyere cheese, gouda cheese, Monterey jack, sharp cheddar cheese, mozzarella cheese, or your favorite melting cheese. I would recommend adding 1 cup to the creamy sauce, then using the remaining 1 cup to sprinkle on top of the casserole.
  • Add fresh or dried herbs such as fresh parsley, dried thyme, Italian seasoning, etc.
  • If you don’t have fresh garlic on hand, use one tablespoon of garlic powder.
  • Stir 1/4 to 1/2 teaspoon of red pepper flakes into the sauce to give the casserole some spice.
  • Add 4 to 6 strips of cooked crispy bacon to the sauce or the top of the casserole for a loaded cauliflower broccoli casserole.

Now that we’re familiar with the healthy ingredients for this amazing Broccoli Cauliflower Casserole that tastes like cheesy goodness, let’s make it!

How to make Broccoli Cauliflower Casserole:

Make the Topping:

Add the avocado oil to a large non-stick skillet and heat to medium-high. Add the sliced onions to the large skillet, sprinkle with sea salt and cover with a lid. Cook covered for about 3 to 5 minutes, until the onions have softened and are beginning to turn golden-brown. Remove the lid and cook for another 5 minutes, stirring occasionally.

Reduce to medium heat or medium-low heat and continue cooking, stirring occasionally, until the onions are deeply golden-brown and caramelized, about 50 to 60 minutes.

Caramelized onions in a nonstick skillet

Once the onions have caramelized, stir in the almond flour until well-combined.

Caramelized onions mixed with almond flour in a skillet

Because this process takes the longest, I recommend starting it first and preparing the rest of the recipe as the onions are caramelized.

Roast the Cauliflower and Broccoli:

Preheat the oven to 375 degrees F and lightly oil a large casserole dish or baking dish.

Wash the broccoli and cauliflower well and pat dry. Remove the stems and chop the head of broccoli and the cauliflower into florets. Transfer the broccoli florets and cauliflower florets to the prepared casserole dish and drizzle with 1 tablespoon of avocado oil.

Casserole dish with raw chopped broccoli and cauliflower in it.

Use your hands to toss everything together until the florets have a light coat of oil. Lightly sprinkle with sea salt. Roast the broccoli and cauliflower in the preheated oven for 35 minutes, until softened and they begin turning golden-brown.

Roasted broccoli and cauliflower in a casserole dish.

While the veggies are roasting, prepare the sauce.

Make the Sauce: 

Add the garlic, full-fat canned coconut milk, cider vinegar and sea salt to a saucepan and bring to a full boil.

Remove the sauce from the heat and allow it to cool for a few minutes. Whisk the egg yolks into the sauce and stir well. Place the skillet back on the stove top and heat over medium-high heat, stirring constantly, until the mixture is steamy and reaches a controlled boil.

Stir in the gluten-free all-purpose flour and continue cooking the sauce for about 3 to 5 more minutes, or until it is very thick and resembles the consistency of custard. Taste the sauce for flavor and add more sea salt and/or cider vinegar to taste.

Creamy dairy-free sauce for casserole in a saucepan.

Prepare the Broccoli Cauliflower Casserole: 

By the time the sauce is ready, the broccoli and cauliflower should be out of the oven (or close to it). 

Pour the sauce over roasted veggies and stir until everything is well-coated in sauce.

Pouring the creamy sauce into the baking dish with the roasted broccoli and cauliflower.

Distribute the caramelized onions over the casserole evenly.

Creamy broccoli and cauliflower with caramelized onion topping spread evenly over it.

Bake at 375 degrees F for 10 more minutes. 

For crispier onions, place the oven on the high broil setting and move the casserole to the second-to-the-top shelf of the oven. Broil for 1 to 3 minutes, until golden-brown and slightly crispy.

Serve the casserole immediately with your main dish or store covered tightly in plastic wrap for up to 5 days prior to serving it. Just be sure to re-heat the casserole in the oven before serving for the best results!

Store any leftover casserole in an airtight container in the refrigerator for up to 1 week.

This yummy casserole tastes even better the next day and the 3-4 days following prep. Ideal for making in advance for your Thanksgiving dinner!

Close up top down image of wooden spoon digging into the cauliflower casserole.

If you’re looking for more healthy side dishes that are ideal for serving many guests, check out these reader favorites.

Healthy Side Dishes:

That’s everything you need to know to make this glorious dairy-free vegetable side dish for your holiday table.

A great way of providing an option for low carb eaters and dairy-free friends alike while still pleasing those with no dietary restrictions.

I hope your family adores it as much as mine does!

Full casserole dish of broccoli cauliflower casserole with caramelized onions on top.

Dairy-Free Broccoli Cauliflower Casserole

Yield: 10 Servings
Prep Time: 15 minutes
Cook Time: 1 hour 10 minutes
Total Time: 1 hour 25 minutes

A dairy-free, low-carb creamy Broccoli Cauliflower Casserole with the most amazing caramelized onion topping. This simple casserole recipe is positively loaded with flavor for a memorable side dish!

Ingredients

  • 1 large head broccoli, chopped into florets
  • 1 head cauliflower, chopped into florets
  • 1 Tbsp avocado oil
  • Sea salt to taste

For the Sauce:

  • 4 cloves garlic
  • 1 (15-oz) can full fat coconut milk
  • 1 Tbsp cider vinegar
  • ½ tsp sea salt, to taste
  • 2 egg yolks
  • 1 Tbsp gluten-free all-purpose flour*

Topping:

  • 2 Tbsp avocado oil
  • 2 large yellow onions, sliced
  • ½ tsp sea salt
  • ½ cup almond flour**

Instructions

Make the Caramelized Onion Topping:

1. Add the avocado oil to a large non-stick skillet and heat to medium-high. Add the sliced onions to the large skillet, sprinkle with sea salt and cover with a lid. Cook covered for about 3 to 5 minutes, until the onions have softened and are beginning to turn golden-brown. Remove the lid and cook for another 5 minutes, stirring occasionally. Reduce to medium heat or medium-low heat and continue cooking, stirring occasionally, until the onions are deeply golden-brown and caramelized, about 50 to 60 minutes.

Caramelized onions in a nonstick skillet

2. Once the onions have caramelized, stir in the almond flour until well-combined.

Caramelized onions mixed with almond flour in a skillet

NOTE: Because this process takes the longest, I recommend starting it first and preparing the rest of the recipe as the onions are caramelized.

Roast the Cauliflower and Broccoli:

1. Preheat the oven to 375 degrees F and lightly oil a large casserole dish or baking dish.

2. Wash the broccoli and cauliflower well and pat dry. Remove the stems and chop the head of broccoli and the cauliflower into florets. Transfer the broccoli florets and cauliflower florets to the prepared casserole dish and drizzle with 1 tablespoon of avocado oil. Use your hands to toss everything together until the florets have a light coat of oil. Lightly sprinkle with sea salt.

Casserole dish with raw chopped broccoli and cauliflower in it.

3. Roast the broccoli and cauliflower in the preheated oven for 35 minutes, until softened and they begin turning golden-brown.

Roasted broccoli and cauliflower in a casserole dish.

While the veggies are roasting, prepare the sauce.

Make the Dairy-Free Cream Sauce: 

1. Add the garlic, full-fat canned coconut milk, cider vinegar and sea salt to a saucepan and bring to a full boil.

2. Remove the sauce from the heat and allow it to cool for a few minutes. Whisk the egg yolks into the sauce and stir well. Place the skillet back on the stove top and heat over medium-high heat, stirring constantly, until the mixture is steamy and reaches a controlled boil.

3. Stir in the gluten-free all-purpose flour and continue cooking the sauce for about 3 to 5 more minutes, or until it is very thick and resembles the consistency of custard. Taste the sauce for flavor and add more sea salt and/or cider vinegar to taste.

Creamy dairy-free sauce for casserole in a saucepan.

Prepare the Broccoli Cauliflower Casserole: 

1. Pour the sauce over roasted veggies and stir until everything is well-coated in sauce.

Pouring the creamy sauce into the baking dish with the roasted broccoli and cauliflower.

Roasted broccoli and cauliflower with sauce mixed in.

2. Distribute the caramelized onions over the casserole evenly.

Creamy broccoli and cauliflower with caramelized onion topping spread evenly over it.

3. Bake at 375 degrees F for 10 minutes. 

4. For crispier onions, place the oven on the high broil setting and move the casserole to the second-to-the-top shelf of the oven. Broil for 1 to 3 minutes, until golden-brown and slightly crispy.

5. Serve the casserole immediately with your main dish or store covered tightly in plastic wrap for up to 5 days prior to serving it. Reheat in the oven at 350 degrees for 20 minutes if you're making this ahead of time.

Horizontal photo of wooden spoon taking a scoop of casserole.

Notes

*Or regular all-purpose flour

**You can also use cassava flour or gluten-free breadcrumbs or regular bread crumbs

Store any leftover casserole in an airtight container in the refrigerator for up to 1 week.

Nutrition Information
Yield 10 Serving Size 1 (of 10)
Amount Per Serving Calories 184Total Fat 14gCarbohydrates 9gNet Carbohydrates 6gFiber 3gSugar 3gProtein 5g

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