Butter, Eggs, and Dairy

When shopping for butter, you can buy salted or unsalted butter. In many markets, you can also buy cultured butter (which has been lightly fermented). We use regular unsalted butter for baking and save cultured butter (either unsalted or salted) for spreading on toast. Butter can pick up off-flavors and turn rancid when kept in the refrigerator for longer than a month. If you don’t use a lot, store butter in the freezer for up to 4 months in a zipper-lock bag and thaw sticks as needed. While some cake recipes call for softened butter, others melt and cool the butter, so pay attention to the instructions.

Our recipes generally call for large eggs. There’s no difference in flavor between white and brown eggs, so use either in your cakes. If your refrigerator has an egg tray on the door, don’t use it. Eggs should be stored on the shelf, where the temperature is below 40 degrees. The average door temperature in our test kitchen refrigerators is closer to 45 degrees. We often call for separating eggs when we want more yolks than whites, like in the New York cheesecake, or when we’re whipping egg whites for volume, like in the fluffy yellow cake.

Some form of liquid dairy is a basic ingredient in many cake batters. In general, we use whole milk (which is 3 1/2 percent fat) in the test kitchen. We have found that low-fat milk (either 2 percent or 1 percent) will work in most baking recipes, but avoid skim.

This tangy dairy product is essential in many cakes. It keeps for several weeks in the refrigerator. If you don't have buttermilk (we prefer to use low-fat), homemade clabbered milk is a good substitute: Add 1 tablespoon of lemon juice to 1 cup of milk and let sit for 10 minutes to thicken. Another option is to use a mixture of 3 parts plain whole-milk or low-fat yogurt and 1 part milk. For instance, use 3/4 cup yogurt plus 1/4 cup milk to replace 1 cup buttermilk. We use buttermilk in the yellow layer cake recipe in this class to add a welcome tang, and provide lift when it reacts with the baking soda.

This thick, tangy dairy product is made from cultured light cream (approximately 18 to 20 percent butterfat). It is pasteurized and then treated with lactic acid-producing bacteria. The bacterial action thickens the cream to a semisolid and gives the sour cream its recognizably piquant flavor. Sour cream has a markedly wet texture—the whey often floats on top—and a light, fleeting mouthfeel. Sour cream makes baked goods rich and moist. You can substitute plain whole-milk yogurt, but the results will be slightly leaner. (Don't use nonfat yogurt; it lacks fat and flavor.) We use just a touch of sour cream for the cheesecake in this class to cut through all the richness.