Salt, Fat, Acid, Heat. Samin Nosrat
to add oil. What is it about oil that yields such moist cakes?
Science holds the answer. 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.
Once I discovered the secrets of oil cake, I could anticipate the qualities of a particular cake without even trying the recipe. If oil was listed among the ingredients, I knew the recipe would yield the signature moist texture I loved so much. But there were times I craved a buttery cake, too. Rich flavour, rather than a moist texture, took priority in cakes I wanted to enjoy in the afternoon with a cup of tea, or serve to friends at brunch. Emboldened by my discoveries about texture, I began to wonder if I could make a better butter cake. The answer lay not in treating butter like oil and melting it, but rather in capitalising on butter’s incredible capacity for lightness.
LIGHT
Lightness might not be the first quality you associate with fat, but its remarkable capacity to entrap air when whipped allows it to act as a leavening, or raising, agent in cakes and transform liquid cream into billowy clouds.
Some classic cakes have no chemical leavening—that is, bicarbonate of soda or baking powder—and rely entirely on whipped fat for their cloudlike structure. In pound cake, whipped butter and eggs do all the work of leavening. In génoise, a type of sponge cake, whipped eggs, whose fatty yolks entrap the air and protein-rich whites surround air pockets, allow the cake to rise. This is the only leavener. There is no baking powder, no bicarbonate of soda, no yeast, and not even any creamed butter to help this cake rise! It is miraculous.
Achieving Lightness: Butter Cakes and Whipped Cream
When seeking rich flavour and a fine, velvety crumb, make a butter cake (or chocolate chip cookies) but take care to aerate this fat by creaming, or whipping, butter with sugar to trap air bubbles for leavening. Typically, cool room-temperature butter is beaten together with sugar for 4 to 7 minutes until the mixture is light and fluffy. When done correctly, the butter will act as a net, entrapping millions of tiny air bubbles throughout the mixture.
The key is to work air in slowly, so that many consistently tiny bubbles form and you don’t create too much heat through friction. It might be tempting to crank up the mixer so you can get the cake into the oven sooner, but trust me—that’ll take you nowhere good, fast. I speak from experience. The road to this chapter is lined with dense, fallen cakes.
As you mix, monitor the butter’s temperature; remember, butter is an emulsion and if it gets too warm, it will melt and the emulsion will break or it simply won’t be rigid enough to continue trapping air. You’ll lose all the air you worked so hard to entrap. If butter is too cold, air won’t be able to get in—not evenly at least—and the cake won’t rise straight up.
And if fat isn’t properly aerated, chemical leavening won’t make up for it. Bicarbonate of soda and baking powder don’t introduce any new air bubbles into a batter. They simply help expand, via the release of carbon dioxide gas, air bubbles already in place.
Incorporating ingredients delicately is important for the same reason—if you go to great lengths to whip air into your fat, then carelessly combine the cake’s dry and wet ingredients, all at once, you’ll lose all of the air you whipped up. This is where folding, the technique of gently combining aerated ingredients into nonaerated ingredients, becomes important. Try to fold using light movements with a rubber spatula in one hand, while spinning the bowl with the other hand.
Though the chemistry behind whipped cream is slightly different than that of whipped butter—it must be very cold, to begin with—the concept at work here is the same: fat surrounds air bubbles. As cream is whipped, solid fat droplets in the liquid break open and join together (remember that cream is a natural emulsion). Overwhip cream and the fat droplets will warm up and continue to stick to one another, making the cream unappetisingly chunky. Whip it further, and cream’s emulsion will break, yielding a watery liquid—buttermilk—and solid fat—butter.
USING FAT
Only on the most special occasions do Persian meals end with dessert, so we never did much baking at our house. Plus, Maman, a health fiend, denied us excess sugar at every turn (though that did little more than encourage my brothers and me to develop fervent sweet tooths). If we wanted cookies or cake, then, we had to make them ourselves, and Maman did her best to ensure it’d be an uphill battle the whole way. She didn’t equip the kitchen with either a stand mixer or a microwave for softening butter, and she stored all the extra butter in the freezer.
When it hit, the craving for cookies or cake was always urgent. I was never patient enough to wait for frozen butter to come up to room temperature, as every single recipe commanded. And even if I did somehow summon the discipline required to wait for butter to soften, without an electric mixer to help cream it, my cookie dough was always a mess—somehow completely overworked and undermixed at the same time, with huge pieces of unincorporated butter. As a typical teenage know-it-all, I knew I was way more clever than any recipe writer. So I figured I could just melt the butter for my baking on the stove and forgo the softening and creaming processes completely. Melted butter was a heck of a lot easier to stir into cookie dough with a wooden spoon, after all, and it sure made cake batter nice and pourable.
What I didn’t know then was that by melting the butter, I was destroying any chance I had at working air into it. My cookies and cakes always emerged from the oven disappointingly flat and dense. At an age when my primary goal in baking was to eat something—anything!—sweet, this was a minor problem: my brothers and I hungrily gobbled up whatever came out of the oven. As an adult with a slightly more discerning palate, I’m going for more than just a hit of sugar. I want my desserts—and, frankly, everything I cook—to be uniformly delicious, with the ideal texture and flavour. You probably do, too. All it takes is a little forethought.
Layering Fats
Since fats have such a powerful impact on flavour, most dishes will benefit from the use of more than one kind. This is what I call layering fats. In addition to considering the cultural appropriateness of a particular fat, think about whether it will harmonise with the other ingredients in a dish. For example, if you’re planning to finish a fish dish with butter sauce, use clarified butter to cook the fish so that the two fats will complement each other. Pair blood oranges with creamy avocado in a salad, then drizzle everything with agrumato olive oil to amplify the citrus flavour. For perfectly crisp waffles, melt butter to add to the batter, but brush the hot iron with fat that’s rendered out of the breakfast bacon.
Sometimes you’ll need to use multiple fats to achieve different textures within a single dish. Deep-fry crisp pieces of fish in grapeseed oil, and then use olive oil to make a creamy Aïoli to serve alongside it. Use oil to make a supremely moist Chocolate Midnight Cake, then slather it in buttercream frosting or softly whipped cream.
Balancing Fat
As with salt, the best way to correct overly fatty food is to rebalance the dish, so the solutions are similar to when you oversalt: add more food to increase total volume, add more acid, water it down, or add starchy or dense ingredients. If possible, chill the dish, let the fat come to the surface and solidify, then skim it off. Alternatively, lift food out of a very greasy pan and dab it on a clean towel, leaving the fat behind.
Foods that are too dry, or need just a bump of richness, can always be corrected with a little olive oil (or other appropriate oil), or another creamy ingredient such as sour cream, crème fraîche, egg yolk, or goat’s cheese to improve the texture and get the flavour right. Use vinaigrette, mayonnaise, a soft, spreadable cheese, or creamy avocado to balance out dryness in a sandwich piled high