Never make our basic chocolate sheet cake when you’re home alone! It’s irresistible: topped with salty pretzels, laced with caramel sauce, set over a superrich buttercream made with caramel sauce, with a light, almost delicate chocolate cake underneath. It’s as if a fine, fancy layer cake batter morphed into a big ol’ sheet cake that will stand up to the incredible caramel/chocolate/pretzel fandango on top.
For the cake
19 tablespoons (2 sticks plus 3 tablespoons) cool unsalted butter, cut into small chunks, plus additional for the sheet pan
2¼ cups plus 2 tablespoons all-purpose flour, plus additional for the sheet pan
6 tablespoons unsweetened cocoa powder
1 cup warm water (about 100°F)
1¼ teaspoons baking soda
½ teaspoon salt
1 cup plus 3 tablespoons granulated white sugar
1 cup plus 3 tablespoons packed light brown sugar
2 large eggs plus 1 large egg white, at room temperature
1 tablespoon vanilla extract
1. Position the rack in the center of the oven. Heat the oven to 350°F. Generously butter and lightly flour the inside of a 13 × 18-inch lipped sheet pan.
2. Whisk the cocoa powder into the water in a small bowl until smooth. Set aside to cool for 30 minutes. Meanwhile, whisk the flour, baking soda, and salt in a medium bowl until uniform.
3. Using a handheld electric mixer or a stand mixer with the paddle attachment, beat the butter and both sugars in a large bowl at medium speed until light, velvety, and fluffy, about 5 minutes. Beat in the eggs one at a time, then beat in the egg white. Scrape down the inside of the bowl, then beat in the sour cream and vanilla until smooth and uniform.
4. With the mixer at low speed, beat in half the flour mixture. Pour in half the cocoa mixture and beat until smooth. Now beat in the remaining flour mixture, followed by the rest of the cocoa mixture. Make sure there are no dry specks of flour down at the bottom of the bowl, then use an offset spatula to spread the thick batter evenly into the prepared pan.
5. Bake until set and a toothpick or cake tester inserted into the center of the cake comes out with a few moist crumbs attached, 18 to 20 minutes. Cool in the pan on a wire rack to room temperature, about 2 hours.
For the buttercream
19 tablespoons (2 sticks plus 3 tablespoons) unsalted butter, softened to room temperature
1¼ cups jarred caramel sauce
⅓ cup full-fat sour cream
1½ teaspoons vanilla extract
2 to 3 cups confectioners’ sugar
3 cups crushed salty pretzels, preferably pretzel nuggets, for topping
1. Using a handheld electric mixer or a stand mixer with the whisk attachment, beat the butter and ¾ cup of the caramel sauce in a clean, dry large bowl until smooth, about 2 minutes. Then beat in the sour cream and vanilla.
2. With the mixer at low speed, beat in 1 cup of the confectioners’ sugar until smooth. Beat in 1 additional cup until smooth. Continue beating, adding more confectioners’ sugar in ¼-cup increments, until the frosting is smooth and spreadable but thick enough to hold its shape on the side of a spatula. Using an offset spatula, spread and smooth the frosting over the cooled cake. Set aside at room temperature to firm up, about 20 minutes.
3. To serve, sprinkle the top of the cake with the crushed pretzels, then drizzle with the remaining ½ cup caramel sauce.
TESTER NOTES
Choose a jarred caramel sauce without a lot of chemical flavor enhancements. Better yet, look for a jarred butterscotch caramel sauce, like an ice cream topping.
