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

In a large bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt until they are well mixed.

Add the eggs, milk, oil, and vanilla extract to the dry ingredients. Mix until everything is just combined and smooth, taking care not to over-mix.

Carefully stir in the boiling water. The batter will be thin, but this is perfectly normal and results in a moist cake.

Divide the batter evenly between the two prepared cake pans.

Bake in the preheated oven for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean.

Let the cakes cool in the pans for about 10 minutes. Then, remove them from the pans and transfer to a wire rack to cool completely.

For the frosting, beat the softened butter with cocoa powder in a bowl until well combined and creamy.

Gradually add the powdered sugar, milk, and vanilla extract while mixing until the frosting is smooth and fluffy.

Once the cakes are completely cool, place one layer on a serving plate, spread some frosting on top, and add the second layer.

Frost the top and sides of the cake with the remaining frosting, swirling it beautifully. Serve and enjoy!