Cake
| 2 cups | Guinness | |
| 2 cups (4 sticks) | unsalted butter | |
| 1 1/2 cups | unsweetened cocoa powder | |
| 4 cups | all purpose flour | |
| 4 cups | sugar | |
| 1 tbsp | baking soda | |
| 1 1/2 tsp | salt | |
| 4 | large eggs | |
| 1 1/3 cups | sour cream |
Preheat oven to 350 F. Butter three 8-inch round cake pans with 2-inch high sides. Line with parchment paper. Butter paper. Bring 2 cups Guinness and 2 cups butter to simmer in heavy large saucepan over medium heat. Add cocoa powder and whisk until mixture is smooth. Cool slightly.
Whisk flour, sugar, baking soda, and salt in large bowl to blend. With an electric mixer, beat eggs and sour cream in a separate large bowl. Add Guinness mixture to egg mixture and beat just to combine. Add flour mixture and beat briefly on low speed. Using rubber spatula, fold batter until completely combined. Divide batter equally among prepared pans. Bake cakes until tester inserted into center of cakes comes out clean; about 35 minutes. Transfer cakes to rack; cool 10 minutes. Turn cakes out onto rack and cool completely.
Icing
| 2 cups | whipping cream | |
| 1 lb | bittersweet or semi-sweet chocolate - NOT UNSWEETENED, chopped |
Bring cream to simmer in heavy medium saucepan. Remove from heat. Add chopped chocolate and whisk until melted and smooth. Refrigerate until icing is spreadable, STIRRING FREQUENTLY, about 2 hours.
Place first cake layer on plate, right-side up. Spread 2/3 cup icing over. Top with second cake layer, upside down. Spread 2/3 cup icing over. Top with third cake layer, right-side up. Spread remaining icing over top and sides of cake.