Must be made in one session, about 1 1/2 hrs.

Stir together all the ingredients except the salt in a heavy 6-quart saucepan with a nonreactive interior. Set the pan over medium-Low heat. Cook 40 minutes, or until the milk reaches 170 F. Keep the heat at medium-low. To keep the curd large, do not stir more than 3 or 4 times. If you lift it with the spatula, you will see sandlike particles of milk forming as the clear whey begins separating from the curd. As the milk comes close to 170, the curds will be slightly larger, about the size of an uncooked lentil. When the temp reaches 170, turn the heat up to medium. Do Not Stir. Take 6 to 8 minutes to bring the mixture to 205-208 when measured at the center of the pot. The liquid whey will be almost clear. By the time cheese comes to 205, the curd should mound on the spatula like a soft white custard. At 205-208 the liquid will be on the verge of boiling, with the surface looking like mounds about to erupt. Turn off the heat and let the cheese stand 10 minutes.

Line a colander with a double thickness of dampened cheesecloth. Turn the mixture into it, and let it drain 15 minutes, or until the drained cheese is thick. Turn the cheese into a covered storage container, add salt if desired, and refrigerate the ricotta until needed.