Place a pizza stone in oven and preheat oven to 450 degrees. Spray a large piece of parchment paper with non-stick baking spray and set aside.
Wash cauliflower, cut off florets, dry thoroughly and add half of the cauliflower to food processor and process until finely chopped, about 30 seconds. Transfer chopped cauliflower to a microwave safe bowl.
Add remaining cauliflower to food processor and again, process until finely chopped, about 30 seconds. Add that cauliflower to bowl with other cauliflower (you should now have about 2 1/2 - 3 cups finely chopped cauliflower).
Cover bowl with microwave safe plastic wrap and heat cauliflower in microwave 4 minutes on HIGH power. Pour cooked cauliflower onto a clean tea towel and allow to cool. Once cauliflower is cool enough to handle, wrap cauliflower in tea towel and wring moisture from cauliflower (about 1/3 cup or so).
Return strained cauliflower to bowl, add parmesan and mozzarella cheese, salt, egg, and garlic and toss mixture with your hands until evenly combined.
Pat mixture into an even round, about 11 to 12-inches, on prepared parchment paper (keeping it snuggly pressed together). Using a pizza peel, transfer crust on parchment to pizza stone in oven and bake 9 - 11 minutes, until golden brown.
Remove from oven and top with pizza sauce, mozzarella and desired toppings (if using fresh herbs, add them after cooking pizza).
Return to oven and bake 5 - 7 minutes longer until cheese has melted and is slightly golden. Allow to cool several minutes then cut into wedges. Serve warm.