I'm not sure If I've ever had chocolate pizza. I have had a pizza pie dessert which i thought was good. but not chocolate i think.
pizza /ˈpiːtsə/ noun a dish of Italian origin, consisting of a flat round base of dough baked with a topping of tomatoes and cheese, typically with added meat, fish, or vegetables. "a cheese and tomato pizza"
just because is in the dictionary doesn't mean that you're doing something illegal by changing the ingredients