01 - Preheat oven to 350°F. Generously grease two 8-inch round cake pans and line bottoms with parchment paper.
02 - Sift flour, sugar, cocoa powder, baking powder, baking soda, and salt into a large mixing bowl.
03 - Add eggs, milk, oil, and vanilla extract to the dry mixture. Beat on medium speed until thoroughly combined and smooth.
04 - Carefully pour in boiling water while mixing. Continue beating until batter becomes glossy and thin in consistency.
05 - Divide batter equally between the prepared pans.
06 - Bake for 30 to 35 minutes until a toothpick inserted into the center emerges clean.
07 - Allow cakes to rest in pans for 10 minutes. Invert onto wire racks and cool completely before frosting.
08 - Beat softened butter until creamy. Gradually sift in powdered sugar and cocoa powder, mixing until fully incorporated.
09 - Blend in vanilla extract and salt. Add milk one tablespoon at a time, beating until frosting achieves smooth, spreadable texture.
10 - Position first cake layer on serving plate. Spread frosting generously over top surface.
11 - Place second layer atop frosted base. Cover top and sides with remaining frosting, smoothing surface with spatula. Decorate as desired before slicing and serving.