Servings: Makes 1 cup
Ingredients 1/2 cup dry mustard powder , preferably one 2-ounce container Coleman's1/2 cup apple cider vinegar2 large egg yolks1/2 cup packed light brown sugar
Whisk mustard powder and vinegar together in a small bowl. Cover and refrigerate overnight.
Whisk yolks and brown sugar into mustard mixture. Transfer to the top of a double boiler and place over simmering water. Cook, whisking constantly, about 8 minutes, until thickened and an instant-read thermometer registers 160°. Remove from heat, cool to room temperature, and chill, covered, until ready to use. (Mustard may be made up to 1 month ahead.)
Adapted from Back to the Table by Art Smith