Take a head of cauliflower and break apart the florets piece by piece. Wash in a colander, then use a grater to grate the florets up to the stems into a large bowl. Alternatively, you could use a food processor.
Grate mozzarella cheese into the same bowl. Add the egg and mix with a spoon.
Layer a pizza pan (or cookie sheet) with parchment paper. Trim the edges of the parchment paper to the shape of the pan so it won't burn in the oven. Spoon on the cauliflower mixture and shape and flatten using your hands. Try to make the crust as thin as possible, spreading the mixture from the centre to the outer sides of the pan evenly.
Bake for 20 minutes or until slightly golden. Remove from oven.
Spoon on a very light layer of pre-made tomato sauce. Sprinkle shredded mozzarella cheese and place on pepperonis and desired toppings.
Bake for another 10 minutes, or until desired readiness, checking crust edges being sure not to burn.
Cut pizza according to portion size preference with a pizza cutter and enjoy!