Chocolate Stout Cake with Dulce de Leche and Vanilla Bean Buttercream

INGREDIENTS

• For Cake:
• 1 1/2 cups (1 bottle) stout or dark beer
• 1 1/2 cups unsalted butter, cut into cubes
• 1 cup dark or dutch-process cocoa powder, sifted
• 3 cups all-purpose flour
• 3 cups granulated sugar
• 2 1/4 teaspoons baking powder
• 1 teaspoon salt
• 3 large eggs, at room temperature
• 2/3 cup sour cream, at room temperature
• For Filling & Frosting:
• 2 cups (4 sticks) unsalted butter, softened and cut into cubes
• 3 3/4 cups powdered sugar, sifted
• 1/4 cup heavy cream
• 1 vanilla bean, scraped
• 2 teaspoons vanilla extract
• pinch of salt
• 3/4 cup dulce de leche, room temperature