Preheat oven to 350 degrees.
Open a can of green enchilada sauce and pour It into a small saucepan. Bring to boil then turn down to medium heat and continue to boil, stirring often to reduce the sauce and thicken it. This takes about 15 minutes.
While the sauce reduces cook cauliflower using your favorite method. I like to steam microwave whole cauliflower heads. Remove outer leaves. Flip cauliflower upside down and run under the faucet. Double wrap cauliflower in plastic wrap so it is completely sealed. Microwave eight minutes for a large cauliflower. Remember, you want the cauliflower to be cooked but not mushy. If your microwave is extra powerful or your cauliflower is small, you may need to reduce the microwave time. After green enchilada sauce has started to thicken add in the cream cheese. Break up the cream cheese with the stirring utensil. Continue to cook the sauce, stirring often until the cream cheese is melted or broken down into tiny pieces (these will melt in the oven).
When the cauliflower has cooled down a little and is safe to handle, cut open the plastic wrap. Open the cauliflower and flip it stem side down onto some paper towels to drain.
Chop drained cauliflower into bite-sized pieces. Season generously with salt, black pepper, and garlic powder.
Add green chile sauce to chopped cauliflower. Add one handful of shredded cheese. Gently stir to combine.
Spray a casserole pan with non-stick spray. Add cauliflower green chile casserole mixture. Top with another handful of shredded cheese.
Bake 25-30 minutes. Remove from oven and let the cauliflower casserole sit on the counter for 10 minutes before serving.