2 large eggs 1 and 1/3 cups all-purpose flour
1/4 cup cornstarch
1/2 teaspoon baking soda
4 teaspoons unsweetened cocoa powder
1/4 teaspoon salt
1/4 cup unsalted butter, softened
1 cup granulated sugar
1/2 cup vegetable oil
2 teaspoons vanilla extract
1/2 teaspoon white vinegar
Red food colouring
1/2 cup buttermilk
Cream cheese frosting
Preheat oven to 350°F (177°C) and line a 12-cup muffin pan with cupcake liners, reserving space for 2 extra cupcakes to bake in a second batch.
Beat 2 egg whites on high speed until soft peaks form (2-3 minutes) and set aside. Sift flour and cornstarch, then whisk with baking soda, cocoa powder, and salt.
Beat butter on high speed until creamy (1 minute), then add sugar and beat for 2 more minutes. Add oil and beat for another 2 minutes. Mix in 2 egg yolks, vanilla, vinegar, and food colouring until combined.
On low speed, alternately add dry ingredients and buttermilk in three parts, starting and ending with dry ingredients. Fold in whipped egg whites until the batter is silky and slightly thick.
Fill liners 1/2 – 2/3 full and bake for 20-21 minutes until a toothpick comes out clean. Cool for 5 minutes in the pan, then completely on a rack. Frost with cream cheese frosting just before serving.