Description
A rich, chocolatey cake baked in a thin sheet pan, topped with a glossy walnut-studded frosting. Ultra-moist from sour cream in the batter, it’s the perfect make-ahead dessert for potlucks or family gatherings.
Ingredients
1 cup margarine
1 cup water
4 tablespoons cocoa powder
2 cups all-purpose flour
2 large eggs, beaten
1 teaspoon baking soda
2 cups granulated sugar
½ cup sour cream
For the frosting
½ cup margarine
6 tablespoons milk
4 tablespoons cocoa powder
1 cup chopped walnuts (optional)
3½ cups powdered sugar
1 teaspoon vanilla extract
Instructions
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Preheat the oven to 375°F. Butter and flour a 10×15×2-inch baking pan or spray it with nonstick spray.
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In a large saucepan over medium heat bring the margarine, water and cocoa powder to a rolling boil.
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Remove the pan from the heat and let the mixture cool for 2–3 minutes.
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Whisk in the flour, beaten eggs, baking soda, granulated sugar and sour cream until the batter is smooth and uniform.
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Pour the batter evenly into the prepared pan.
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Bake on the center rack for 22–25 minutes, or until a toothpick inserted in the center comes out clean.
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Allow the cake to cool in the pan for 10–15 minutes while you make the frosting.
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For the frosting, combine margarine, milk and cocoa powder in a saucepan and bring to a boil.
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Remove from heat and immediately stir in the chopped walnuts, powdered sugar and vanilla until the frosting is smooth and spreadable.
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Pour the warm frosting over the cake and spread evenly with a spatula.
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Let the cake sit at room temperature until the frosting is set, about 1 hour, then cut into squares to serve.
Notes
Leftover cake can be stored in an airtight container at room temperature for up to 3 days.
For a nut-free version omit the walnuts or substitute toasted pecans.
To make the cake even more moist, swap half the sour cream for plain Greek yogurt.
If your kitchen is cool and the frosting firms too quickly, warm it briefly before spreading.