Preheat oven to 350 degrees. Rice 1 head of cauliflower in a food processor until grain consistency. Take 2 cups of riced cauliflower and microwave for 4 minutes (this is to get rid of the extra moisture). Let cool until able to handle.
Once cooled, mix into riced cauliflower; 1 whole eggs, 1/2 cup mozzarella, 2 Tablespoon chopped scallions, and season to taste with salt, pepper, garlic powder, and oregano.
Spray a baking sheet with cooking oil and pour cauliflower mixture onto baking sheet. Form into a disk (the thinner it is, the crispier). Bake at 350 degrees for 10 minutes until golden brown.
In a medium skillet, cut open sausage casing to break up and cook sausage until done. Place the ground up chicken sausage in a separate bowl.
Slice the yellow onion and cook in a drizzle of Olive Oil until caramelized, then throw in chopped mushrooms to also cook down. Take off heat when done.
Assemble your pizza! Pour 2 TBSP of tomato sauce onto the crust, sprinkle caramelized onions, ground chicken sausage, mushrooms, and mozzarella on top. Bake for 3-4 minutes or broil for 1-2 minutes. Top with more fresh cut scallions, enjoy!