Preheat your oven to 350°F (175°C) and prepare two 8-inch heart-shaped cake pans with parchment paper and grease.

In a large mixing bowl, whisk together all-purpose flour, granulated sugar, cocoa powder, baking powder, and salt for about two minutes.

Add softened unsalted butter to the dry ingredients and mix until the texture resembles damp sand, about 2-3 minutes.

In another bowl, whisk together egg whites, buttermilk, vegetable oil, and vanilla extract. Pour into dry ingredients and mix until smooth.

Divide batter evenly between prepared pans. Bake for 32-35 minutes or until a toothpick comes out with a few moist crumbs.

Cool cakes in pans for 10 minutes, then transfer to the freezer for 30 minutes.

Prepare chocolate buttercream by beating softened unsalted butter until creamy, then adding powdered sugar, cocoa powder, salt, heavy cream, and vanilla. Beat until smooth and fluffy.

Once cakes are cool, layer them with chocolate buttercream in between, and frost the entire cake.