Deep, dark and totally chocolaty, just call this cake pure comfort food. The smooth, shiny ganache that frosts the cake is easily made with just two ingredients—semisweet chocolate and whipping cream.
1. Preheat oven to 350F. Grease and flour two 9 x 2-inch round cake pans. In a saucepan, melt butter and unsweetened chocolate, stirring, over low heat. Set aside; cool slightly.
2. Combine flour, sugar, cocoa, baking soda and salt in a large bowl of electric mixer. Add chocolate mixture, buttermilk and eggs. Beat at low speed for 1 minute; increase speed to high and beat until light and fluffy, about 2 minutes.
3. Divide batter equally between prepared pans. Bake until cakes spring back when gently pressed, 35–40 minutes. Cool in pans 5 minutes; invert onto wire racks.
4. Bring cream just to a boil. Remove from heat and stir in chocolate chips; mix until frosting is smooth and starts to thicken.
5. Place 1 cooled layer on a cake plate. Spread top with 1/3 cup frosting. Top with second layer. Frost top and side of cake with remaining frosting.