Preheat oven to 400 degrees F. Grease a pizza pan or use a pizza stone.
Chop cauliflower into florets. Add to a food processor and pulse until it becomes crumbly. Put into a microwave safe bowl and cook in microwave for 2-3 minutes until tender. Allow to cool on a clean dish towel.
Once cooled, squeeze out any excess moisture by wringing the cauliflower inside the towel. Transfer cauliflower into a clean mixing bowl.
Grate the cheese; add 1/4 cup of the mozzarella, Parmesan, basil, parsley, oregano, salt, and pepper into the bowl. Toss to combine, and then add the egg. Stir until completely mixed together.
Place "dough" onto a greased pizza pan or pizza stone. Shape into crust, making it thicker than you would for a regular pizza crust. Set aside. Place into oven and bake for 15-20 minutes, or until golden.
Slice olives, dice pepper and cut mushrooms into smaller pieces. Spread pizza sauce over crust and sprinkle with toppings and remaining cheese.
Place pizza back into oven and bake for 10 minutes. Allow to slightly cool before serving.