When my friends in New York compliment my buttermilk pie, I tell them this: In the South, you learn how to bake before you learn how to fry. And then you learn how to walk.
This light, lemony, sweet-yet-tangy custard pie always sells out when it’s on my menu. Its flavor recalls a time before refrigeration, when sweet milk wouldn’t keep in the summer heat. Instead, people used the slightly sour liquid that remained after milk was churned to butter.
Nowadays, the buttermilk you buy at the supermarket is made from milk that’s cultured and fermented until it thickens slightly and takes on that tart flavor that makes much of southern baking—and this pie—so wonderful.
Pay attention to your whites, and use a whisk
When some of my customers see buttermilk pie on the menu, they think of chess pie, another southern classic. Although some versions of chess pie seem similar, my buttermilk pie is nothing like the chess pie I had growing up. In my experience, that pie is a denser, sweeter confection, often with cornmeal in the filling, and found mostly at church bake sales.
My buttermilk pie, on the other hand, is far less sweet and gets its tartness reinforced with a squeeze of lemon. More important, egg whites whipped to soft peaks lighten the custard. A slice of this pie reveals a thick, soufflé-like layer resting on a thinner, creamier layer. When you take a bite, you get the best of both: the silky-smooth mouth-feel of the creamy layer and the this-feels-so-light-I-could-eat-it-all-day benefit of the fluffy top layer.
Separate the eggs while cold; whisk at room temperature. When an egg is cold, the white will separate more readily from the yolk, and the yolk is less likely to rupture during the process. But although egg whites separate better just out of the fridge, they whip to their maximum volume at room temperature, in part because the surface tension of the white is lower at room temperature, making it easier for small air pockets to form.
Because egg whites can’t mix to their maximum volume if they come into contact with any fat beyond the trace they already contain, you’ll want to be sure your bowl—preferably stainless steel; copper is even better—and your whisk are absolutely greasefree. For the same reason, if you do get even a speck of egg yolk in your white, remove it with a knife, or use that egg for scrambling and crack another for this recipe.
It’s better to err on the side of underwhipping than over. For a filling with the best texture and optimum volume, you want to mix the whites to incorporate air without overmixing them.
You can whip the egg whites with an electric mixer, but I recommend whipping them by hand because it’s too easy to overmix with a machine. Either way start slowly to create small air bubbles, which are more stable than large ones, and then go ahead and whisk more vigorously. Stop whisking the egg whites when you can lift away the whisk and see a definite peak. If the peak droops a little, that’s fine: slightly underwhipped egg whites will do less damage than overwhipped ones, which, because the protein bonds have broken, are no longer able to give the pie filling structure. Whites mixed just right will hold a definite shape; overmixed whites will look dull and clumpy.
Gently fold the egg whites and the custard together. When folding the whites and the custard together, use a spatula and a gentle motion to avoid deflating those egg whites that you whipped so carefully.
For the tastiest, flakiest crust, use butter, shortening, and lard
The key to this delicious and incredibly flaky pie crust is the three different fats used. For a truly southern pie, lard is a must. Made from rendered, clarified pork fat, lard makes the flakiest pie crusts. It’s available at the supermarket (or you can render your own from freshly trimmed pork fat), and it has a mild, nutlike flavor. Solid at room temperature, lard gives you the same flakiness as vegetable shortening but also adds a richness of flavor that shortening lacks. If you can’t get your hands on lard, or if you’re a vegetarian, substitute vegetable shortening for the amount of lard called for, and just don’t tell your southern friends.