Chocolate–Blackberry Mousse Cakes
Serves: 18
 
Ingredients
  • 1⁄2 cup unsalted butter, softened
  • 3⁄4 cup granulated sugar
  • 2 large eggs
  • 1 teaspoon vanilla extract
  • 1 1⁄2 cups plus 2 tablespoons cake flour
  • 1⁄4 cup unsweetened cocoa powder
  • 3⁄4 teaspoon baking soda
  • 1⁄2 teaspoon fine sea salt
  • 1⁄3 cup whole buttermilk
  • 1⁄3 cup boiling water
  • 1⁄4 cup seedless blackberry preserves
  • Blackberry Mousse (recipe follows)
  • Bittersweet Chocolate Ganache (recipe follows)
  • Garnish: fresh blackberries and rosemary sprigs
Instructions
  1. Preheat oven to 350°. Spray a 15 1⁄4x10 1⁄4x3⁄4-inch rimmed baking sheet with cooking spray. Line with parchment paper and spray again.
  2. In a large bowl, beat together butter and sugar with a mixer at medium-high speed until light and fluffy, 3 to 4 minutes. Scrape down sides of bowl. Add eggs, one at a time, beating well after each addition. Beat in vanilla extract.
  3. In a fine mesh sieve set over a medium bowl, sift together flour, cocoa powder, baking soda, and salt into bowl. Gradually add flour mixture to butter mixture alternately with buttermilk, beginning and ending with flour mixture, beating just until combined after each addition. Carefully add 1⁄3 cup boiling water; beat until combined. Spread batter into prepared baking sheet, smoothing with an offset spatula to create a level surface. Tap baking sheet gently on countertop to settle batter and reduce air bubbles.
  4. Bake until a wooden pick inserted in center comes out clean, 9 to 11 minutes. Let cake cool completely in baking sheet. Cut cake in half width-wise and remove parchment paper. (Each cake half should measure approximately 9 1⁄4x7 1⁄4 inches.)
  5. To assemble cake, place a cake half on a cutting surface, right side up.
  6. In a small pan, gently warm blackberry preserves over low heat, stirring until smooth. Using a pastry brush, spread a very thin layer of warm preserves over cake, covering completely.
  7. Place cake in freezer until preserves are cooled and set, 3 to 5 minutes.
  8. Using an offset spatula, spread mousse in an even layer over preserves layer. Top with remaining cake half, right side up. Using an offset spatula, spread warm ganache on top of cake, creating ripples for texture, if desired.
  9. Place cake in freezer and freeze until firm, approximately 4 hours.
  10. Using a long sharp knife and pressing downward for clean cuts, cut away uneven edges from all sides of frozen cake, running knife blade under hot water and wiping clean between each cut. Cut cake in thirds lengthwise and in 6 rows widthwise to create 18 cake rectangles. Store cakes in an airtight container in the refrigerator and serve within a day. Let cakes come to room temperature for best texture and flavor before serving.
  11. Just before serving, garnish with fresh blackberries and rosemary, if desired.
Recipe by TeaTime Magazine at https://teatimemagazine.com/chocolate-blackberry-mousse-cakes/