How Milk Upgrades Store-Bought Cake Mix

Boxed cake mix is not only one of the easiest but also one of the most economical ways to make a cake since you generally don't have to add anything more than a few eggs, some water, and an inexpensive type of neutral-tasting oil such as vegetable or canola. Of course, you can always upgrade your cake by swapping out some of the ingredients and, if you're using milk in place of water, it might even be a thrifty move. Sure, water is (more or less) free if it comes straight out of your tap, but milk that's just starting to sour can be used to make a cake once it gets to the point where you no longer want to pour it on your cereal.

So what does using milk do for your cake? Since it contains a certain amount of fat, it not only boosts the flavor but also gives the cake a denser texture, which is closer to what you'd find in a scratch-made cake. If you prefer a cake that's extra-airy, though, you're better off skipping the milk swap and lightening up your boxed cake mix with a fizzy can of soda, instead.

While you can use any type of milk in a cake mix — whole, 2%, skim, plant-based, or even chocolate — many bakers swear by buttermilk. Even though this ingredient may not produce any kind of detectable tanginess, the extra acidity will break down the gluten and make for a more tender cake. (If you don't care for the stuff and are unlikely to drink up the leftovers, you can make a decent buttermilk substitute by acidifying a cup of regular milk with a tablespoon of lemon juice or distilled white vinegar.) Yet another way to achieve this effect is by adding sour cream to your boxed mix (half a cup should do) as this doesn't just boosts the batter's lactic acid content but also provides flavorful fat.

The water isn't the only liquid you can substitute on a boxed cake mix, since the oil, too is something that can be replaced with a dairy product. Butter is an obvious choice — either melt or soften an equal amount of butter and then stir it into the mix in place of the oil. Yogurt, too, can be used, but if you go for an extra-thick kind like Greek yogurt, you'll need extra to compensate for the missing liquid. If your cake calls for half a cup of oil, as many mixes do, half a cup plus 2 tablespoons of thick yogurt should work in its place.