This recipe is by Martha Stewart.
- 8 ounces bittersweet chocolate (preferably 61 percent cacao), chopped
- 1 1/4 cups heavy cream
- 2 tablespoons good-quality ground espresso beans
- 1 cup all-purpose flour, plus more for parchment paper
- 3/4 teaspoon salt
- 1/3 cup unsweetened Dutch-process cocoa powder
- 1/2 cup (1 stick) unsalted butter, softened
- 1/4 cup sugar
- 3/4 teaspoon pure vanilla extract
- 3 tablespoons heavy cream
- 1 1/2 cups mascarpone cheese
- 1 large egg
LET'S MAKE THE TART:
- Make the ganache: Put chocolate into a medium heatproof bowl, and set aside. Bring cream and espresso to a boil in a small pan. Pour through a fine sieve over the chocolate; discard solids. Let stand 2 minutes, then whisk until smooth. Let cool to room temperature, 1 to 2 hours.
- Make the tart shell: Sift flour, salt, and cocoa powder into a medium bowl; set aside. Put butter and sugar into the bowl of an electric mixer fitted with the paddle attachment; mix on medium speed until pale and fluffy, about 4 minutes. Add egg and vanilla, and mix until combined, scraping down sides of bowl as needed. Reduce speed to low. Gradually add the flour mixture in 3 batches, alternating with the cream. Shape dough into a thick rectangle; wrap in plastic. Refrigerate until cold, about 30 minutes.
- Preheat oven to 350 degrees. Roll out dough between 2 pieces of lightly floured parchment paper to a 16-by-6-inch rectangle, about 1/4 inch thick. Press dough into a 14-by-4 1/2-inch rectangular flan frame set on a baking sheet lined with parchment. Trim dough flush with top edge. Prick all over bottom of shell with a fork. Bake until firm, 18 to 20 minutes. Transfer to a wire rack; let cool completely. Unmold.
- Put ganache into the bowl of an electric mixer fitted with the whisk attachment; beat on medium-high speed until soft peaks form, about 4 minutes. Transfer to a pastry bag fitted with a large star tip (such as Ateco No. 828).
- Smooth mascarpone cheese over bottom of tart shell with an offset spatula.
- Pipe ganache rosettes, one next to the other, on top of mascarpone to cover.