Preheat oven to 350°F (175°C). Grease and line two round cake pans with parchment paper.

In a bowl, whisk together flour, cocoa powder, sugar, baking powder, and salt.

In another bowl, beat eggs until frothy; add milk, vegetable oil, and vanilla extract.

Combine wet and dry ingredients, stirring gently until just mixed.

Divide batter into prepared pans and bake for 30-35 minutes or until a toothpick comes out clean.

Cool cakes in pans for about 10 minutes before transferring to wire racks.

For frosting, beat softened butter until creamy; gradually mix in powdered sugar and cocoa powder.

Add heavy cream to reach desired consistency.

Frost cooled cakes generously and serve.