Total time: 25 minutes, plus 1½ to 2 days setting and draining times
Servings: This makes a generous cup of quark.
2 cups whole milk
1/2 cup cultured buttermilk
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.
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 crème fraîche, about 1 day.
3. Transfer 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.
4. Use as desired. To store, place the cheese in a glass, ceramic or plastic container. Cover and refrigerate up to four days.