Preheat oven to 400F. Oil a 9-inch cast iron skillet; place skillet in oven to heat while preparing crust.
Cut or break the cauliflower into large florets. Steam cauliflower in a steamer basket; drain well and squeeze out excess liquid by placing in a clean dishcloth.
Process cauliflower in a food processor a until they very finely chopped. Transfer to a large bowl.
Add the cheese, egg, and (optional) salt and pepper to the chopped cauliflower; mix thoroughly until well-blended.
Using oven mitts, remove skillet from oven (be careful! It will be VERY hot). Spoon and spread the cauliflower mixture into the skillet until it is even.
Return skillet to oven and bake for 23 to 28 minutes until golden brown at the edges.
Using oven mitts again, remove skillet from oven; spread/top with desired toppings.
Return skillet to oven and bake for 5 to 10 minutes longer.
Cut into pieces and serve!