Makes enough to frost a 6-inch (two-layer) cake)
½ cup milk
½ teaspoon vanilla extract
tablespoons (18 grams) flour
½ cup (112 grams |1 stick) butter, softened
½ cup (100 grams) granulated natural cane sugar
Combine the milk, extract and flour in small pot over medium heat. Cook, whisking constantly, until mixture has thickened considerably, almost pudding-like, about 2 minutes. Remove from heat. Pour into a bowl, press a piece of plastic film onto the thickened milk so a “skin” doesn’t form. Set in a cold spot to cool completely.
Meanwhile, add the butter and sugar to a bowl. Beat until creamy, 3 to 5 minutes. Scrape the cooled milk mixture into the bowl. Beat until light & fluffy, about 5 minutes. Use immediately, or store in the fridge up to 3 days. Bring to temperature before using.