Sweet Potato Cake With Toasted Marshmallow Frosting
★★★★★
PREP TIME
4 hours
COOK TIME
40 minutes
MAKES
one 13x9-inch cake
Ingredients
2 3/4 cups
all-purpose flour
1 3/4 teaspoons
baking powder
1 teaspoon
kosher salt
1/4 teaspoon
baking soda
2 teaspoons
ground cinnamon
3/4 teaspoon
ground nutmeg
1/2 teaspoon
ground ginger
1/4 teaspoon
ground allspice
1 cup
vegetable oil
1 1/2 cups
light brown sugar
1 cup
granulated sugar
2 teaspoons
pure vanilla extract
3
large eggs
1
large egg yolk
2 cups
sweet potato purée (from about 1 pound whole potatoes, or canned)
3
large egg whites
1 1/2 cups
granulated sugar
1 1/2 teaspoons
light corn syrup
1/2 teaspoon
cream of tartar
1/4 teaspoon
kosher salt
1/4 cup
water
1 teaspoon
pure vanilla extract
Instructions
- To make the cake, heat the oven to 350°F. Grease a 13x9x2-inch pan with non-stick spray or soft butter. Line the bottom with parchment paper.
- In a medium-sized bowl, whisk together the flour, baking powder, salt, baking soda, and spices.
- In a large bowl, whisk together the oil, sugars, and vanilla. Add the eggs and yolk, one at a time, and continue whisking until smooth. Add the sweet potato and whisk again.
- Add the dry ingredients to the wet in three installments and, using a rubber spatula, gently fold to combine just until the flour disappears—do not over-mix.
- Transfer the batter to the prepared pan and smooth the top with an offset spatula or butter knife. Bake for 30 to 35 minutes, rotating at the halfway point, until a cake tester comes out with a moist crumb or two.
- Let cool until easy to handle, then run a butter knife around the edges, releasing it from the pan. Invert the cake onto a cooling rack, flipping it right side up to cool to room temperature.
- At this point, the cake will keep at room temperature, tightly wrapped, for up to 2 days. Hold on the frosting until you’re ready to eat.
- To make the frosting, add the egg whites, sugar, corn syrup, cream of tartar, salt, and water to the bowl of a stand mixer and place the bowl over a saucepan of simmering water over medium heat. Do not allow the bottom of the bowl to touch the water.
- Whisk constantly until the sugar melts and the mixture is warm to the touch, 3 to 5 minutes. Remove the bowl from the heat and place the bowl on the stand mixer fitted with the whisk attachment. Beat the egg white mixture on high speed until stiff and glossy, 5 to 7 minutes. Add the vanilla and continue beating until just combined.
- Use a spoon or offset spatula to generously frost the cake. Toast the frosting using a kitchen torch or by placing the frosted cake under the broiler briefly, until browned.
- The frosted cake is best served within a few hours, as the frosting loses structure over time, but any leftovers will keep on the counter lightly covered for up to 1 day.
