Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a large mixing bowl, combine all-purpose flour, cocoa powder, granulated sugar, baking powder, baking soda, and salt. Whisk until fully blended.

Add eggs, whole milk, vegetable oil, and vanilla extract to the dry mixture. Mix with a hand mixer until smooth.

Carefully stir in boiling water to the batter. The batter will be thin but this enhances moisture.

Pour the batter into prepared pans, filling each halfway. Tap gently to release air bubbles.

Bake in the oven for 30-35 minutes, testing for doneness with a toothpick.

Allow the cakes to cool in the pans for 10 minutes, then invert onto wire racks to cool completely.

Cream together unsalted butter until smooth. Gradually mix in extra cocoa powder and powdered sugar, alternating with milk, until creamy.

Once cakes are cool, place one layer on a serving plate, spread frosting on top, and stack the second layer. Coat with remaining frosting.

Slice and enjoy your beautifully frosted cake, ready for any occasion.