2 c. stout (such as Guinness)
2 c. butter
1 1/2 c. unsweetened cocoa powder
4 c. flour
4 c. sugar
1 Tbsp. baking soda
1 1/2 tsp. salt
4 large eggs
1 1/3 c. sour cream
2 cups whipping cream
1 pound bittersweet (not unsweetened) or semisweet chocolate, chopped
Preheat oven to 350°F. Butter three 8-inch cake pans. Line with parchment. Butter paper.
Bring stout and butter to simmer in large saucepant. Add cocoa powder and whisk until smooth. Cool slightly.
Whisk flour, sugar, baking soda, and 1 1/2 teaspoons salt in large bowl to blend. Using electric mixer, beat eggs and sour cream 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. Divide batter equally among prepared pans. Bake cakes about 35 minutes. Transfer cakes to rack; cool 10 minutes. Turn cakes out onto rack and cool completely.
Bring cream to simmer in medium saucepan. Add chopped chocolate and whisk until melted and smooth. Refrigerate until icing is spreadable.
Ice cake, when completely cool, and serve.