adapted from the Barrington Brewery in Great Barrington, MA via Smitten Kitchen
1/2 cup stout (such as Guinness)
1/2 cup (1 stick) unsalted butter
1/4 cup plus 2 tablespoons raw cacao or unsweetened cocoa powder
1 cup all purpose flour
1 cup sugar
3/4 teaspoon baking soda
1/2 teaspoon sea salt
1 large egg
1/3 cup whole milk yogurt
4 ounces good semisweet chocolate
1/4 cup heavy cream
1/2 teaspoon coffee grounds
Whipped Cream (optional)
1/2 cup heavy cream
1/2 teaspoon vanilla extract
1 tablespoon powdered sugar
Preheat oven to 350°F. Butter and flour your pan and add a sheet of parchment for the easiest removal.
Bring 1/2 cup stout and 1 stick butter to simmer in heavy medium saucepan over medium heat. Sift in cacao or cocoa powder to remove lumps and whisk until mixture is smooth. Cool slightly.
Sift flour, sugar, baking soda, and salt into a large bowl. Using an electric mixer, beat egg and yogurt in another large bowl to blend. Add stout-chocolate mixture to egg mixture and beat just to combine. Add flour mixture and beat briefly on slow speed. Using rubber spatula, fold batter until completely combined.
Pour batter into prepared pan. Bake cake until tester inserted into center comes out clean, about 30 minutes. Transfer cake to rack; cool completely, then turn cake out onto rack for assembling.
For the ganache, melt the chocolate, heavy cream, and coffee preferably in the top of a double boiler over simmering water until smooth and warm, stirring occasionally (I just put it directly into a pot and stir almost constantly) .
If you are making a small, rectangular layer cake and baked your cake in a 9" x 13" pan, cut the cake in half and place one half on a cake platter or plate. Add a layer of whipped cream only on top of the cake. Carefully place the second layer onto the whipped cream. At this point, the frosting of the cake works best if you refrigerate the cake for at least one hour. This is a good trick to prevent the cake from losing crumbs into the frosting.
Once cake is cold, frost the sides and top using the ganache. It is possible you may have to slightly warm the ganache in order to get it to spread.