Heat oven to 350°F. Line two 8 inch round baking pans with parchment paper and then spray lightly with non-stick cooking spray. Set aside.
Stir together sugar, flour, cocoa, baking powder, baking soda and salt in large bowl.
Add eggs, milk, oil and vanilla and mix until well combined.
Stir in boiling water (or hot coffee). Batter will be thin, but that's okay! Pour batter into prepared pans.
Bake 30 to 35 minutes or until a toothpick inserted in the center of the cake comes out clean.
Combine butter and cocoa powder.
Add powdered sugar, milk, and vanilla extract. Mix for several minutes until smooth and fluffy.
Place one cake layer on serving tray. Spread a generous amount of frosting on top. Add second cake layer. Frost top and sides of cake with remaining frosting.
Cut and serve.
One Layer Cake:Grease 9x13'' pan with non-stick cooking spray. Pour batter into prepared pan. Bake at 350 degrees F. for 35 to 40 minutes. Cool completely. Frost.Cupcakes:Line cupcake pan with paper liners and fill 2/3 full with batter. Bake cupcakes for 22 to 25 minutes. Cool completely completely before frosting. Makes 24-30 cupcakesBundt Cake: Properly grease and flour the pan and cook the chocolate cake for about 50-55 minutes. Cool for 15 minutes in the pan before inverting onto a wire cooling rack.Make Ahead and Freezing Instructions: The cakes and the chocolate frosting can both be made ahead of time. Allow the cakes to cool completely and then wrap each layer in plastic wrap and place in a freezer bag. Freeze for up to three month. Cakes can be frosted while frozen.The homemade chocolate frosting will keep well in an air-tight container in the fridge for up to two weeks, or in the freezer for up to three months. Remove the frosting from the fridge about an hour before you’re ready to frost your cake to allow it to come to room temperature.