Step 1 In a stainless steel, heavy-bottomed saucepan, bring the milk to a simmer over medium heat. Remove from heat and set aside until the milk is cooled. Whisk in the buttermilk.
Step 2 Transfer the mixture to a glass, ceramic or plastic container, and set aside at room temperature until the mixture is thickened, with a consistency similar to yogurt or creme fraiche, about 1 day.
Step 3Transfer the mixture to a cheesecloth-lined strainer set over a bowl. Refrigerate overnight to drain the whey from the cheese; the whey should be clear, not cloudy, as it is drained.
Step 4Use as desired. To store, place the cheese in a glass, ceramic or plastic container. Cover and refrigerate up to four days.