[carlob]

> A calzone should have ricotta cheese not mozzarella.

It typically has both. And ricotta is legally not a cheese in Italy (because it's not made from milk).

[socalgal2]

I thought Ricotta is what's left over after you make another cheese from milk, most commonly cows milk.

Wikipedia says ricotta is made from milk in Italy from the production of mozzarella

[carlob]

Yeah, pretty much this. But the law in Italy defines cheese as something made directly from milk, whereas ricotta is made mostly from whey (you can add some milk, but it's secondary).

Similarly things like mascarpone and yogurt which are not fermented using rennet can't be called cheese.

Regarding the type of whey used to make ricotta it can come from any cheese. In central Italy sheep ricotta is more prized than cow, but you can easily find buffalo and goat ricotta as well.

[pimlottc]

Whey leftover from Parmesan production is also commonly used to make ricotta