Cocoa powder and melted chocolate give this classic Chocolate Sheet Cake with Vanilla Buttercream deep, well-rounded flavor. Inspired by devil’s food cake, it's a party-perfect dessert that's rich but not overly sweet. 

Martha Stewart Living, June 2019


Read the full recipe after the video.

Recipe Summary

30 mins
1 hr 10 mins
Serves 12 to 16


Ingredient Checklist


Instructions Checklist
  • Preheat oven to 350 degrees. Butter a 9-by-13-inch baking pan. Line bottom with parchment; butter parchment. Stir together boiling water, cocoa, and chocolate; let cool 10 minutes. Meanwhile, whisk together flour, baking powder, baking soda, and salt in another bowl.

  • Beat butter with sugar on medium-high speed until fluffy, 2 to 3 minutes. Beat in eggs, one at a time, beating to combine after each addition and scraping down sides of bowl as needed. Beat in vanilla, then chocolate mixture. Reduce speed to low; beat in flour mixture in two batches, alternating with sour cream, until just combined. Scrape batter into prepared pan, smoothing top with an offset spatula.

  • Bake until a tester inserted in center comes out with a few moist crumbs, 35 to 40 minutes (top will not spring back). Let cool in pan 10 minutes. Invert onto a wire rack and remove parchment; let cool completely. Cake can be made up to 1 day ahead and stored at room temperature, wrapped in plastic.

  • Spread buttercream evenly over top and sides of cake. Sprinkle with chocolate curls. (Leftovers can be refrigerated, wrapped in plastic, up to 3 days; return to room temperature before serving.)

Cook's Notes

To make the chocolate curls, pop a semisweet chocolate bar (we like Ghirardelli) in the microwave on a plate to soften, 5 to 10 seconds. Then shave into curls with a vegetable peeler directly over the cake, or onto a parchment-lined baking sheet.