Article: While the cake is cooling, mix together 4 tablespoons (57 g) of butter, 2 tablespoons (12 g) of cocoa powder, 1 cup (156 g) of powdered sugar, and teaspoon (2.5 ml) of vanilla in a medium size bowl. Stir until all of the ingredients are well blended. You don't necessarily have to make a chocolate frosting for the cookie cake. Use your favorite buttercream frosting recipe for a simple vanilla frosting if you prefer. You can also use canned frosting in your favorite flavor if you're short on time. Once the butter mixture is well blended, begin stirring in 1 to 2 tablespoons (15 to 30 ml) of milk. You only want to add as much milk as is necessary to make the frosting smooth. Whole milk works best for the frosting, but you can use whatever type you prefer. After you've finished mixing the frosting, place it in a piping bag that's fitted with a decorative tip. Carefully pipe the frosting along the outer edge of the cookie cake in whatever pattern you prefer. Make sure that the cake has cooled before you pipe the frosting onto it. The frosting may melt otherwise. If you don't have a piping bag, you can place the frosting in a sealed plastic bag and cut the tip off one of the bottom corners. Squeeze the bag so the frosting emerges from the hole just as it would through the tip of a piping bag. To make the cake more festive for the occasion, use the chocolate frosting in the piping bag or a tube of decorating gel to write "Happy Birthday" or a similar message on the cake. If you're using a piping bag, you may need to switch to a smaller tip when you're writing. If you want a more colorful look for the cake, press some bright sprinkles, colored sugar, or dragees into the frosting. Colorful candies, such as M&M's, also make ideal decorations for the cake. Shaved chocolate and mini chocolate chips are also fun decorations for the cake.

What is a summary?
Combine the butter, cocoa powder, powdered sugar, and vanilla. Add milk until the frosting is smooth. Place the frosting in a piping bag and pipe along the edges of the cake. Use the frosting or a decorating gel to write on the cake. Accent the cake with sprinkles.