Occasionally, I am absolutely seized by an overwhelming, out-of-the-blue urge to make a chocolate cake—a real cake, with two layers and chocolate frosting like the one Bruce Bogtrotter eats in Matilda, and big plans to eat fat slices cold from the fridge (which is the best way to eat chocolate cake, if you ask me).
I have flirted with recipes here and there, but the one that hangs in my memory like the Ghost of Good Cakes Passed is one my mother made: boxed chocolate cake mix beefed up with boxed chocolate pudding mix, sour cream, and hot coffee, with a slick of marmalade between the layers and orange zest in the chocolate frosting. Part of this is the winning combination of flavors—chocolate and orange, I mean, c’mon—but part of it is in the cake’s texture: Tender and moist and light all at once.
I had never made the connection between the oil called for on the box of cake mix and the cake’s unbeatable tenderness—just as Samin Nosrat, author of the cookbook Salt, Fat, Acid, Heat, came to connect the dots between carrot cake, olive oil cake, Chez Panisse’s Fresh Ginger and Molasses Cake, and her friend Lori’s Chocolate Midnight Cake: Oil (and specifically, a combination of oil and water), not butter, is the key to super-moist, light-textured cakes. Butter, on the other hand, makes for rich and richly flavored pound cakes, polenta cakes, and other cakes that are just right for a cup of tea in the afternoon.
Why? Samin turns to science to break it down:
“Oil efficiently coats flour proteins and prevents strong gluten networks from forming, much like soft butter does in shortbread. Gluten development requires water, so this oil barrier significantly inhibits gluten formation, leading to a tender, rather than chewy, texture. As an added bonus, less gluten means more water in the batter, and, ultimately, a moister cake.”
Realizing this helped Samin predict what a cake’s texture might be just by looking at the recipe—and now we can too. Substituting oil for butter in a cake recipe one-for-one may have mixed results; you’ll have to experiment a little if you want to try swapping in a favorite recipe. But while you may not know the exact measurement of oil needed, you will be able to anticipate what the cake’s crumb will be like.
What’s more, making the switch from butter to oil changes things up big time in the flavor department, freeing the cake from capital-B Butteriness. Not like butteriness is bad, of course—but in addition to the textural properties butter lends, it has a distinctive taste that can fog up the mirror for other flavors. Trade butter for a neutral oil like safflower or sunflower or another vegetable oil and the cake’s flavor—sunshiney lemon or deep chocolate or toasty espresso or sweet, delicate coconut—will sing clearly.
And neutral oil is only the beginning: A coconut cake will be made only more coconutty with coconut oil. Pistachio oil would make for a nuanced, curious vanilla cake (especially if some ground pistachios found their way into the batter). And grassy olive oil would play up the flavors in a lemon and rosemary cake. This is another benefit of oil cakes: The oil is yet another flavor variable to play with. If you're looking for a few cakes to try out a swap (you're studying!), here are a few to start with: