Preheat oven to 400 F.
Boil heavy cream until thickened. Add white pepper and the juice from a half of a lemon. Slice onion very thin so that you are left with rings. Saute onion rings in olive oil until they are starting to get brown.
Assemble pizza as follows:
Unroll pizza dough onto a non-stick pizza pan. Add cheese, then prosciutto. Add the cream mixture at a time to the pizza, a tablespoon at a time, forming little puddles spread around the pizza. Drain the onions and put them on last. They will continue to carmelize as the pizza bakes.
Bake 8-10 minutes. Don't over bake. You don't want to "dry out" the pizza.