If you didn't know already, I have an absolute obsession with cake. Coconut Cake, Ice Cream Cake, Polenta Cake . . . it doesn't matter—I love it all! But sometimes nothing will do except rich, moist chocolate cake slathered with creamy, chocolate buttercream frosting, and this cake is exactly that. It's at once homey, impressive, and deeply satisfying to eat. Adults and kids both love it because . . . chocolate. It's the cake that strikes that nostalgic pang in my heart when I think of childhood birthday celebrations with balloons and streamers in primary colors. So go ahead: Make the time investment, bake this Chocolate Birthday Cake with Chocolate Frosting and eat your heart out, even if it's only your un-birthday.

Notes: I used the cake batter to make 12 cupcakes, (for a birthday play-date with a few besties,) and a small 6-inch double layer cake to enjoy with the family. I've also included instructions for using the batter to make all cupcakes, a 9x13 cake, or an 8-inch 3-Layer cake: Don't be scared off by all the text! I love the included recipe for Chocolate Buttercream Frosting because it stays beautifully shiny and creamy even as it sits out, and it's not cloyingly sweet. If the frosting begins to curdle as you are beating it, switch to high speed and keep whipping it until it looks smooth again. Don't worry, just keep whipping, and I promise it will come together. The cake is best at room temperature and will keep for 3 days without refrigeration . . . if it lasts that long!

Read More: The Shared Chocolate Birthday Cake

Time: 2 hours
Yield: 12 cupcakes + 6-inch double-layer cake (I used a 6x3" round pan), 30 cupcakes, 13x9x2-inch baking pan, or 3-layer cake (8" rounds)

2 cups sugar
1 3/4 cups all-purpose flour
3/4 cup cocoa (natural, not dutch process)
1 teaspoon baking powder
1 1/2 teaspoons baking soda
1 1/2 teaspoons kosher salt (3/4 teaspoon table salt)
2 eggs
1 cup shaken buttermilk
1/2 cup vegetable oil
2 teaspoons vanilla extract
1 cup very hot brewed coffee
1 recipe Chocolate Buttercream Frosting (See recipe below.)
Loads of sprinkles

Preheat oven to 350 degrees F. Cupcakes: Line with cupcake liners. Cake pans: Cut parchment paper to fit the bottom of the pans. (I trace the bottom of the pan onto the parchment paper, then cut it out for a perfect fit.) Grease the bottoms and sides of the pan(s), line with the parchment paper, then grease the top of the parchment paper. (The extra parchment paper step ensures no wasted effort from the cake sticking to the pan!)

In a large bowl (or stand-mixer bowl fitted with a flat beater), stir together sugar, flour, cocoa, baking soda, baking powder, and salt. Beat in eggs, buttermilk, oil, and vanilla at medium speed for 2 minutes, until well-combined. Stir in very hot coffee - batter will be runny. Pour batter into prepared pans, filling them 2/3 full.

Bake until a wooden toothpick poked into the middle of the cake comes out clean. (Cupcakes: 22 to 25 minutes, 6x3-inch round: 30-35 minutes, 9x13-inch cake: 35-40 minutes, three 8-inch round cake pans: 30-35 minutes.) Cool 10 minutes, then remove from pans to wire racks. Cool completely. 

Cupcakes: Frost with Chocolate Buttercream Frosting and decorate judiciously with sprinkles!

6-inch Double Layer Cake: If necessary, lightly trim the top of the cake to create a flat top. Using a serrated bread knife, slice the cake horizontally to create two round layers of equal thickness. Place one layer on a flat plate or cake stand. Using a knife or offset spatula, spread the top with frosting. Top with the second layer, and spread frosting all over the top and sides, creating pretty swirls as you go, if you like. Decorate with plenty of sprinkles!

13x9 Single-Layer Cake: Spread Chocolate Buttercream Frosting over the top and sides. (There will be extra frosting.) Then sprinkle, sprinkle, sprinkle with sprinkles!

3-Layer Cake: Lightly trim the top of each 8" round cake to create a flat top. Place one layer on a plate or cake stand. Using a knife or offset spatula, spread the top with frosting leaving a 1/4" border. Top with the second layer, and spread the top with frosting leaving a 1/4" border. Place the final layer on top, and spread frosting evenly over the top and sides, creating pretty swirls as you go, if you like. Then, go crazy with those sprinkles!

Chocolate Buttercream Frosting

Recipe adapted from The Cake Bible by Rose Levy Bernanbaum

10 ounces bittersweet or semisweet chocolate, roughly chopped or chips
2 cups unsalted butter, room temperature (softened)
4 large egg whites, room temperature*
1 cup granulated sugar

Using a double-boiler to melt chocolate: Improvise a double-boiler, (if you don't have one,) by filling a saucepan 1/4 full with water and placing a heat-safe bowl over the pot. (The bowl should not touch the water.) Bring the water to a boil, then reduce the heat to low to keep a steady simmer. Place the chocolate into the bowl and stir frequently, until the chocolate begins to melt. Remove from heat when half the chocolate is melted, and continue to stir, using residual heat to complete the melting. The chocolate should be completely smooth. (If the chocolate is not completely melted, return the chocolate to the double-boiler for 30 seconds and continue stirring.)

Using a microwave to melt chocolate: Microwave chocolate in a microwave-safe bowl on high for 15 seconds. Stir well. Repeat until chocolate is half-melted and stir, using residual heat to complete the melting. If chocolate cools before chocolate is completely smooth, return to the microwave for another 15 seconds and continue to stir until chocolate is fully melted.

In a mixing bowl beat the butter on medium speed until smooth and creamy.

In the bowl of an electric mixer, beat the egg whites using the whisk attachment, (if you have one,) using a high speed setting, until soft peaks form when the beater is raised. Gradually beat in the sugar until stiff peaks form when the beater is raised slowly. Beat in the butter by the tablespoon. If the mixture looks slightly curdled, increase the speed a little and beat until smooth before continuing to add more butter. Add the melted and cooled chocolate all at once and beat until smooth and uniform in color. Use immediately or place in an airtight bowl. Re-beat frosting at room temperature to restore texture.

*Contains raw egg: Please be aware that consuming raw and lightly cooked eggs exposes a slight risk of salmonella or other food-borne illness. To reduce this risk, use fresh, properly refrigerated, clean grade A or AA eggs with intact shells, and avoid contact between the yolks or whites and the shell.