For the Cake:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or line them with parchment paper.

2. Mix Dry Ingredients: In a large bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.

3. Add Wet Ingredients: Add the eggs, milk, vegetable oil, and vanilla extract to the dry ingredients. Mix until well combined.

4. Incorporate Boiling Water: Slowly add the boiling water to the batter, stirring until smooth. The batter will be thin, but this will give the cake its moist texture.

5. Bake: Divide the batter evenly between the prepared cake pans. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.

6. Cool: Let the cakes cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely before frosting.

For the Frosting:

1. Make the Frosting: In a medium saucepan, melt the butter over medium heat. Add the cocoa powder and whisk until smooth.

2. Combine: Gradually add the powdered sugar, milk, vanilla extract, and salt to the cocoa mixture. Stir until smooth and well combined.

3. Cool Slightly: Allow the frosting to cool for a few minutes before spreading it on the cooled cake.

Assemble the Cake:

1. Layer the Cake: Place one layer of the cooled cake on a serving platter. Spread a generous amount of frosting over the top.

2. Top with Second Layer: Place the second cake layer on top, and spread the remaining frosting evenly over the top and sides of the cake.

3. Serve: Let the frosting set for a few minutes before slicing and serving. Enjoy!