Fudgy Chocolate Pretzel Cake

Ingredients

• For the cake:
• 4 ounces bittersweet chocolate, finely chopped
• 1 1/2 cups hot coffee
• 1 1/2 cups light brown sugar
• 1 1/2 cups granulated sugar
• 1 1/4 teaspoons salt
• 3 large eggs
• 3/4 cup oil
• 1 1/2 cups sour cream
• 1 tablespoon vanilla extract
• 2 1/2 cups all-purpose flour
• 1 1/2 cups cocoa
• 2 teaspoons baking soda
• 3/4 teaspoon baking powder
• For the frosting:
• 13 tablespoons unsalted butter, softened
• 5 ounces bittersweet chocolate, melted and slightly cooled
• 2/3 cup plus 1/4 cup sour cream
• 7 tablespoons cocoa
• 2 teaspoons vanilla extract
• 3 cups confectioners' sugar
• 3 ounces pretzel knots, crushed, divided

Directions

1. Set a rack in the center of the oven, then heat the oven to 350 degrees F. Grease 2 9-inch cake pans and line them with parchment paper. Put the chocolate in a large bowl, pour the coffee over it, and whisk until the chocolate has melted. Let it cool briefly. Whisk in the brown sugar, granulated sugar, salt, eggs, oil, sour cream, and vanilla until everything is combined. In a medium bowl, whisk together the flour, cocoa, baking soda, and baking powder. Add the dry mixture to the wet mixture and whisk until smooth. Divide the batter evenly between the pans and bake for 35 to 40 minutes, until the cakes are just set and a toothpick inserted in the center comes out with moist crumbs. Leave the cakes in their pans for 30 minutes, then turn them out onto wire racks to cool all the way.
2. Using a mixer fitted with the paddle, mix the butter, chocolate, sour cream, cocoa, and vanilla on low speed until combined. Add the sugar and mix just until incorporated. Turn the speed up to medium and beat until creamy, about 1 minute. If the frosting is too soft to spread over the cake, chill it briefly until it thickens.
3. Set 1 cake on a serving plate and spread about 2/3 cup frosting over it. Scatter almost half of the crushed pretzels over the frosting, then set the second cake on top, rounded side up. Use the remaining frosting to cover the top and sides of the cake. Sprinkle the remaining pretzels over the top.