Sorry, I couldn't help myself (so sooo punny!). Why the "whole" in the title? Ricotta is actually traditionally made from the whey left over after cheesemaking, hence the "ri" (re) "cotta" (cooked). You acidify the whey or wait until it has acidified naturally after sitting for a few hours at room temp (the cultures from your first batch of cheese are still working away in there!) and then heat until the remaining curd begins to precipitate from the whey.