For cake:

Preheat oven to 350°F. Spray or grease a 12-cup Bundt Pan, making sure to get fat into all the nooks and crannies.

In a medium-sized saucepan over medium heat, bring Guinness to a simmer. Add cocoa powder and espresso powder, and whisk until the mixture is smooth. Cool slightly.

In a large bowl, whisk the flour, sugar, baking soda, and salt.

In another bowl, whisk the eggs, oil, buttermilk, and vanilla, whisking hard to ensure the eggs are well incorporated. Add the stout-chocolate mixture to the egg mixture and beat well to combine. Add the wet ingredients to the flour ingredients and gently incorporate them, do not over-mix.

Pour into prepared bundt pan. Bake cake for about 45-50 minutes. The key to a moist cake is not over to bake.

Cool for about 15 minutes, then tip the cake onto a wire rack to cool completely.

For frosting:

Bring cream to a simmer in a heavy medium saucepan, do not boil or burn. Place chocolate in a medium bowl. Add the hot cream to the chocolate, and let it sit on the chocolate for about 1 minute. Add the whiskey, vanilla, and salt. Whisk until melted and smooth. Leave room temperature until frosting is thick but still pourable and thickened, frequently stirring, about 30 minutes. It may take longer, depending on the temperature of your kitchen.

Place the cake on a serving dish or cake stand. Pour the frosting over the cake until it flows over the sides. Let set for 1-2 hours before serving.

See, super easy peasy.