Preheat oven to 350°F (175°C). Grease two 9-inch round cake pans thoroughly with butter, then dust with cocoa powder. Line bottoms with parchment paper for easy release.
In a large bowl, whisk together flour, sugar, cocoa powder, baking soda, baking powder, and salt until evenly distributed.
2 cups all-purpose flour, 2 cups granulated sugar, 3/4 cup unsweetened Dutch-processed cocoa powder, 2 teaspoons baking soda, 1 teaspoon baking powder, 1 teaspoon salt
In another bowl, whisk together eggs, buttermilk, oil, and vanilla until smooth and well combined.
2 large eggs, 1 cup buttermilk, 1/2 cup vegetable oil, 2 teaspoons pure vanilla extract
Add wet ingredients to dry ingredients, mixing until just combined. Don't overmix to avoid tough cake texture.
Slowly whisk in hot coffee until batter becomes smooth and thin. The thin consistency is normal and creates moist cake layers.
1 cup hot brewed coffee
Divide batter evenly between prepared pans. Bake for 28-32 minutes, or until a toothpick inserted in center comes out with just a few moist crumbs.
Let cakes cool in pans for 15 minutes, then turn out onto wire racks to cool completely before frosting.
Melt chopped dark chocolate with heavy cream using double boiler or microwave in 30-second intervals. Stir until completely smooth and glossy. Let cool slightly.
8 oz semi-sweet dark chocolate, 1 cup heavy cream
Beat softened butter until light and fluffy. Gradually add sifted powdered sugar, vanilla, and salt. Beat until smooth, then slowly incorporate melted chocolate mixture.
1/2 cup unsalted butter, 2 cups powdered sugar, 1 teaspoon vanilla extract, 1 pinch salt
Level cake layers with serrated knife if needed. Place first layer on serving plate and spread generous amount of frosting on top.
Add second layer and apply thin crumb coat of frosting all over cake. Chill for 30 minutes to set.
Apply remaining frosting generously to top and sides. Create decorative swirls or smooth finish to match iconic movie appearance.