Preheat the oven to 400 degrees F and lightly oil a large casserole dish.

Wash the cauliflower well and pat dry. Remove the green stems, chop cauliflower into florets and add to the prepared casserole dish. Roast cauliflower in the preheated oven for 35 minutes, until it begins turning golden-brown.

While the cauliflower is roasting, prepare the sauce. Add 2 tablespoons of avocado oil to a large skillet and add the chopped onion. Sauté onion, stirring occasionally until it begins to brown, about 10 minutes. Add the garlic and coconut milk and bring to a full boil. Cook at a full boil, stirring occasionally for 2 minutes, until thick and the sauce pulls away from the pan when stirred.

Remove Sauce from heat and allow it to cool for 3 minutes. Whisk the egg yolks in a bowl, add into the sauce mixture and stir well. Place the skillet back on the stove top and heat over medium-high again and heat until mixture is steamy but not boiling. Stir in the cider vinegar and 1 cup of the grated cheese and stir until melted and thick. Remove sauce from the heat. Taste sauce for flavor and add more sea salt and/or cider vinegar to taste.

Pour the sauce over roasted cauliflower. Stir the sauce into the cauliflower very well until everything is well-coated in sauce. Sprinkle with the remaining 1 cup of cheese.

Bake at 425 for for 5 to 6 minutes, until the cheese is melted.

Change oven to 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 cheese is golden-brown and slightly crispy.

Sprinkle casserole with chopped green onion and sprinkle with black pepper. Serve!