Overnight Homemade Crema (buttermilk version)
Makes 1 cup
1 cup (228 grams) heavy cream
1 tablespoon2 (30 grams) buttermilk
Add the cream to a glass, microwave-safe mason jar. Heat on high for 45 seconds, until the cream is luke warm (about 95ºF). Stir in the buttermilk.
Cover the jar with a piece of cheesecloth or paper towel. Screw the ring closure on top (leave the lid off). Line a loaf pan with a kitchen towel. Place the jar in the pan, and wrap the towel around it. Set the pan in a warm spot until the cream thickens, anywhere from 18 to 24 hours. Refrigerate the crema, and use within 2 weeks.