Heat one tablespoon of avocado oil (or olive oil) in a large skillet (I use a 12-inch skillet) or a large thick bottomed pot such as a Dutch oven over medium-high heat. Add the chopped onion and sauté for 2 to 3 minutes, until the onion begins to soften.
Stir in the mushrooms and garlic and sprinkle with a little sea salt. Sauté, stirring occasionally, until the mushrooms begin to leach water.
Add in the gluten-free flour and stir until it appears as though it has mostly dissolved.
Pour the full fat coconut milk, broth, cider vinegar, Worcestershire sauce, and dijon mustard into the skillet (or pot) and bring the mixture to a full boil.
Transfer this creamy mushroom mixture to your crock pot.
Wipe out the skillet (or pot) and add the remaining 1 tablespoon of oil. Heat over high heat and allow the skillet to heat up for a few minutes. Once hot, carefully place the beef stew meat onto the skillet in a single layer. Sear for 2 to 3 minutes on two sides.
Transfer the seared beef to the slow cooker with the sauce mixture. Give everything a big stir. Secure the lid on the crock pot and slow cook on High heat for 3.5 hours or Low heat for 7.5 hours.
After the initial cooking time is up, open the lid, give everything a stir, then stir in the pasta noodles.
Replace the cover and continue cooking on high heat for 20 to 30 minutes, or until the pasta noodles have cooked through but are still slightly al dente.
Serve beef stroganoff in big bowls with a sprinkle of chopped fresh parsley.