Preheat oven to 350 degrees.
Cook the cauliflower in the microwave according to the package instructions. Remove the cauliflower from the microwave and create a mash using an immersion blender or you can add the cauliflower to a high-powered blender and blend for 30-45 seconds until the cauliflower becomes soft and mashed.
Heat a skillet on medium-high heat with olive oil. Add the onions and garlic. Cook for 2-3 minutes until the onions become soft and fragrant.
Add the cream cheese, sour cream, and 1 cup of the cheddar cheese. Season with salt, pepper, cumin, and chili powder. Stir and cook for a couple of minutes until the cheese melts.
Add in the shredded chicken and stir.
Spray a 9X13 baking dish with cooking oil. Create a layer of the chicken and cheese mixture.
Next, layer on the cauliflower mash.
Top with the enchilada sauce and 1 cup of shredded cheddar.
Bake for 15-20 minutes until the cheese has fully melted.
Allow the casserole to cool completely before slicing. If you cut into it too soon, it will feel like you are scooping out mush. This is a soft casserole in comparison to most casseroles. Keep that in mind, the top layer is mashed cauliflower. It will harden more as it stands and even more so after being refrigerated.