I give a lot of credit to those ballsy vegetables that sneak their way into baked goods. Carrots and zucchini—even the occasional beet and parsnip—cozy up to sugar and butter and become shadows (delicious, irresistible shadows) of their once virtuous selves. And the sweet potato? The sweet potato doesn't even try to disguise its intentions: with a name like that, it was destined for baking.
A key ingredient in Southern cooking traditions, sweet potatoes have made their way into casseroles, pies, and breads. Originally from the Caribbean and South America, sweet potatoes were brought back to Europe by Christopher Columbus, who said they "looked like yams and tasted like chestnuts." While overseas, they gained popularity sliced and candied; meanwhile, in the Americas they remained a simple and affordable staple food frequently distributed as slave rations. But by the mid-19th century the crop gained mass appeal and became a shared tradition of the South as the cuisine became more homogenous.
Sweet potatoes were a primary food of the poor because they were easy to grow, inexpensive, and offered a lot of nutrients. Initially, they entered the world of baking as a way to extend flour in foods like biscuits: refined wheat flour was expensive and the now common biscuit was considered a food for the well-to-do. Today, we don't add mashed sweet potatoes to biscuits for necessity, we do it because it tastes so good.
Why Sweet Potatoes Work
Don't be deceived. Despite the name, sweet potatoes aren't all that sweet. (Nor are the finished biscuits from this recipe.) Sweet potatoes are made up almost entirely of starch, which in turn is made up of simple sugars. While starch doesn't taste sweet, once heat is added, enzymes break down the starch into maltose, a simple disaccharide (sugar) that's about a third as sweet as table sugar, which contributes a rich flavor and mild notes of sweetness to the biscuit dough.
Sweet potatoes also add natural moisture to the dough while helping to maintain the biscuits' fluffy texture. The moisture-absorbing nature of the starch, meanwhile, provides some structure to the biscuits.
Sweet Potato Biscuit, Step-By-Step
Step 1: Roast the potato
To roast sweet potatoes as a sophisticated side dish, check out this sweet recipe. But for this recipe, simply placing them on a baking sheet in a 400°F oven for 45 minutes to 1 hour is enough. Allow the roasted sweet potato to cool completely. This can be done the day before.
Step 2: Mash the potato
Although you can certainly use a food processor for this step to create a smooth purée, I prefer to mash the sweet potato by hand. Doing this "the rustic way" gives the biscuits lots of texture and preserves small pieces of sweet potato that offer little bursts of flavor.
Step 3: Combine wet ingredients
Whisk the potato purée with heavy cream and buttermilk. The acidity of the buttermilk adds flavor, while the full fat from the heavy cream gives the biscuits additional tenderness and richness.
Step 4: Whisk those dry ingredients
In a large bowl, whisk the flour, salt, sugar, and baking powder. Whisking the dry ingredients kills two birds with one stone: It mixes the ingredients thoroughly, while also aerating them. Sifting/whisking is important when it comes to making biscuits fluffy and light because it ensures that all of the ingredients are nicely distributed throughout the batter.
Step 5: Cut in the Butter
Using a knife or bench knife, chop the butter into lima bean-sized pieces. Toss the butter into the dry ingredients. Using your fingers (or a pastry blender) rub the butter into the dry ingredients until the mixture resembles coarse meal. Do this quickly, so the heat of your hands doesn't melt the butter.
Step 6: Mix it!
Add the sweet potato and dairy mix to the party. Using a spatula, gently stir 5 to 6 times, or until the mixture is fully hydrated. The dough should look shaggy and wet. Since some of the flour has been replaced with sweet potato, these biscuits have less risk of becoming tough because there is less gluten.
Step 7: Scoop it!
Using a teaspoon (or small ice cream scoop), scoop walnut-sized balls of dough onto a sheet pan.
Step 8: Bake!
Brush the portioned biscuits with melted butter and bake 'em at 400°F for about 20 minutes, or until the bottoms become brown and the tops turn slightly golden.