Step 1 In a heavy saucepan, warm the milk, buttermilk and nutmeg over high heat. Stir the mixture frequently until it reaches 120 degrees (warm to the touch), about 2 to 3 minutes.
Step 2 Stir occasionally; the milk will begin to separate. When it reaches 175 degrees to 180 degrees, about 1 to 2 minutes, gently scrape the bottom of the saucepan. The curds will rise to the top. Cook at 180 degrees for 1 minute.
Step 3Line a strainer or colander with cheesecloth and place it over a bowl or pot large enough to catch the liquid from the cheese. Pour the contents of the saucepan into the strainer. Gently stir in the Parmesan and salt while the mixture is still hot. Gather up the corners of the cheesecloth and tie it up with string. Let it drain for 15 minutes. Once the ricotta is at room temperature, transfer it to an airtight container and store it in the refrigerator until ready to use. Makes 1 cup.