Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a large mixing bowl, sift together the flour, sugar, cocoa powder, baking powder, baking soda, and salt. This ensures a smooth and evenly textured cake.
Add the eggs, milk, oil, and vanilla extract to the dry ingredients. Beat on medium speed for about 2 minutes until the batter is well combined.
Gradually add the boiling water to the batter, mixing on low speed. The batter will be thin, but this is normal.
Pour the batter evenly into the prepared cake pans.
Bake in the preheated oven for 30 to 35 minutes or until a toothpick inserted into the center comes out clean. The baking time may vary, so start checking for doneness around 25 minutes.
Allow the cakes to cool in the pans for 10 minutes before transferring them to a wire rack to cool completely.
While the cakes are cooling, prepare the chocolate frosting. In a large bowl, beat the softened butter until creamy. Add the cocoa powder, powdered sugar, milk, vanilla extract, and a pinch of salt. Beat on low speed until the ingredients are combined, then increase the speed to medium and beat until the frosting is smooth and fluffy.
Once the cakes are completely cooled, spread a layer of chocolate frosting on top of one cake layer. Place the second cake layer on top and frost the entire cake with the remaining chocolate frosting.
Decorate the cake as desired or leave it with a classic, rustic finish.
Slice, serve, and enjoy this delicious homemade chocolate cake!