Preheat oven to 450 degrees.
Line a baking sheet with parchment paper.
Steam the cauliflower until it is very soft.
Cool slightly and then squeeze out as much moisture as possible. (I like to literally wring out the cauliflower in a tea towel.) Transfer to a food processor and process until smooth.
Add the egg whites, 1 cup of mozzarella cheese, herbs and salt. Process until combined, scraping down sides as needed.
Spread the mixture in an even layer on the prepared baking sheet or pizza stone.
Bake for about 18-20 minutes or until the crust begins to turn a darker golden brown around the edges with spots on top.
Remove from the oven, then add desired sauce, toppings, and remainder of cheese.
Return to oven for 10-12 minutes or until toppings are heated through and cheese is melted and golden.