01 - Preheat oven to 350°F. Grease and flour two 9-inch round cake pans, ensuring even coverage to prevent sticking.
02 - In a large mixing bowl, sift together the all-purpose flour, cocoa powder, granulated sugar, baking powder, baking soda, and salt until well blended.
03 - Add the eggs, whole milk, vegetable oil, and vanilla extract to the dry mixture. Beat on medium speed for 2 minutes until the batter is smooth and free of lumps.
04 - Gradually pour in the boiling water while mixing until fully combined. The batter will appear thin — this is expected and ensures a moist result.
05 - Pour the batter evenly between the two prepared cake pans, tapping gently on the counter to release any trapped air bubbles.
06 - Bake for 30 to 35 minutes, or until a toothpick inserted into the center of each layer comes out clean. Avoid overbaking to retain moisture.
07 - Allow the cakes to cool in their pans for 10 minutes, then carefully invert onto wire racks to cool completely before frosting.
08 - Beat the softened butter until light and creamy. Sift in the powdered sugar and cocoa powder, then add the milk and vanilla extract. Beat until the frosting is smooth and fluffy.
09 - Place one cake layer on a serving plate and spread frosting evenly over the top. Position the second layer on top and frost the entire outside of the cake, smoothing the sides and top with an offset spatula.