Preheat and Prepare Pans:

Heat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans, ensuring they are fully coated to prevent sticking.

Mix Dry Ingredients:

In a large bowl, sift together the sugar, flour, cocoa, baking soda, baking powder, and salt. Stir until evenly combined.

Combine Wet Ingredients:

Add the eggs, milk, vegetable oil, and vanilla extract to the dry mixture. Use an electric mixer to beat the ingredients on medium speed for about 3 minutes, until smooth and creamy. Gently fold in the boiling water by hand, which will result in a thin batter.

Bake the Cake:

Divide the batter evenly between the prepared pans. Bake for 30 to 35 minutes, or until a toothpick inserted in the center comes out clean. Allow the cakes to cool in the pans for 10 minutes before transferring them to a wire rack to cool completely.

Prepare the Frosting:

While the cakes cool, use an electric mixer to cream the softened butter until light and fluffy. Gradually add the powdered sugar and cocoa powder, alternating with the milk and vanilla, beating until the frosting reaches a smooth, spreadable consistency.

Assemble the Cake:

Once the cake layers have fully cooled, carefully slice them horizontally to create four layers. Spread an even layer of frosting over the top of each layer as you stack them. Finish by frosting the outside of the assembled cake, ensuring even coverage.

Serve and Enjoy:

Your rich, chocolatey creation is now ready to be sliced and enjoyed!