In a pinch for decoration ideas, I used some chocolate chips turned up-side down around the edge, along with a dusting of powdered sugar.
Chocolate Cake with Milk Chocolate FrostingAdapted from makes two 9 inch cake layers or 16 cupcakes
cake2 ounces chocolate (61 to 70 percent cocoa solids)1/2 cup plus 2 tablespoons cocoa1 teaspoon vanilla extract16 tablespoons (8 ounces) butter, at room temperature1 1/2 cups sugar3 whole eggs, at room temperature1 egg yolk, at room temperature2 cups plus 1 tablespoon flour3 teaspoons baking powder1/2 teaspoon salt
frosting10 ounces milk chocolate1/2 cup heavy cream1/4 teaspoon salt3/4 cup powdered sugar16 tablespoons (8 ounces) butter, slightly chilled
Preheat the oven to 350˚ and position rack in the middle of the oven. Grease and lightly flour tow 9 inch cake pans or 16 muffin tins.
Make the chocolate and cocoa syrup. Chop the chocolate into 1/2 inch pieces and combine with the cocoa in a medium sized bowl. Bring 1 cup of water to a boil and gently whisk half of the hot water into the chopped chocolate. Whisk in the remaining hot water and continue whisking until you have a shiny, thick, smooth chocolate syrup, 2 minutes. Add the vanilla extract. Set the syrup aside and allow it to come to room temperature.
Cream the butter and incorporate the eggs. Place the butter in the bowl of a stand mixer with the paddle attachment and beat on medium speed for one minute. Add the sugar and beat on medium-high speed until the mixture becomes fluffy and almost white in color, 6-8 minutes, stopping the mixer occasionally to scrap down the sides of the bowl. Add the whole eggs one at a time, and continue to beat until they are fully incorporated. Add the egg yolk and beat until the batter looks smooth and glossy, 30 seconds.
In a dry bowl, whisk together the dry ingredients.
With the mixer on slow speed, add half the flour mixture to the butter mixture and beat until the flour is just incorporated. Add all the chocolate syrup and continue mixing on slow speed. Add the second half of the dry ingredients and beat until batter is thoroughly combined. Scrap down the sides with a spatula and beat the batter on medium speed for 20 seconds.
Scrape the batter into the prepared pans, evening out the batter with a rubber spatula. Run a pairing knife in a single circular motion through the batter, 1 inch from the edge of the pan. This will help the cake rise evenly (not too sure this worked very well for me, my cakes still domed a little). Bake the cakes until the center set and and a tester comes out clean, approximately 25-30 minutes. If you are making cupcakes, bake them for 20-25 minutes.
Allow the cakes to cool on wire racks for about 20 minutes. Run a paring knife around the outer sides of the pan and invert the cakes onto cooling racks. Allow the cake layers to cool to room temperature.
To make the frosting, melt chocolate in a double broiler. Remove the bowl from heat. Heat the cream in a small saucepan. Add the hot cream to the melted chocolate, whisking continuously, to make a shiny, smooth ganache. Place the bowl of ganache in the refrigerator, scraping the bowl with a rubber spatula every 5 minutes, until the ganche is slightly chilled, around 60˚F.
In the bowl of a stand mixer, whisk the slightly chilled ganche together with the salt, powdered sugar, and the slightly chilled butter on medium speed for 4-6 minutes. The icing should hold the lines of a whisk, increase in volume, and become a much lighter shade of brown.
Fill and ice the cake. If the cake layers domed a bit too much, use a long serrated knife to trim the peaked tops to even out the tops. Place the bottom layer on a decorative serving plate. Cut a 12-inch long piece of wax paper into 4 equal strips. Place each strip under an edge of the cake to cover the rim of the plate, to prevent it from becoming coated with icing. Using an off set spatula, smear a generous layer of icing over the bottom cake layer, making sure to smear an equal amount of icing around the outer edge of the layer. Place the second cake layer on top. Evenly ice the whole cake with the remaining icing. Once you have smoothed out all the rough edges, remove the wax paper strips from underneath the cake to reveal a spotless serving platter beneath your finished cake.
Serve the cake at room temperature. The cake will keep, covered at room temperature, for 4 days. If it's very hot in your kitchen, store the cake, covered, in the refrigerator but serve at room temperature.