- 1 cup (2 sticks) unsalted butter, cut into pieces, plus more for baking sheets
- 8 ounces best-quality bittersweet chocolate, coarsely chopped
- 1 teaspoon instant espresso powder
- 4 large eggs, room temperature
- 1 cup granulated sugar
- 1 cup firmly packed dark-brown sugar
- 2 teaspoons pure vanilla extract
- 3/4 teaspoon fine sea salt
- 1 cup all-purpose flour, sifted
- Ganache for mocha fudge brownies
- 1. Preheat oven to 350 degrees. Lightly coat with butter two 8 1/2-by-12-inch rimmed baking sheets, and line with parchment paper; set aside.
- 2. Combine butter and chocolate in a medium heatproof bowl. Place over a saucepan of simmering water. Stir occasionally until melted. Stir in espresso powder. Remove from heat; set aside.
- 3. In the bowl of an electric mixer fitted with the whisk attachment, combine eggs, sugars, vanilla, and salt. Whisk to combine. Add the chocolate mixture, and whisk to combine. Add flour, and whisk until just combined. Divide batter evenly between prepared baking sheets, using an offset spatula to smooth the surface. Bake, rotating baking sheets, until a shiny crust appears on the surface and the center is still soft when a cake tester is inserted into the center, 12 to 15 minutes. Transfer to a wire rack to cool to room temperature, about 1 hour.
- 4. Invert brownies onto parchment paperâ€“lined cutting boards, and remove parchment. Re-invert brownies onto parchment paperâ€“lined cutting boards. Place one of the brownies in the refrigerator to chill for 1 hour. Let remaining brownie stand, covered at room temperature, for 1 hour. Spread room temperature brownie evenly with ganache. Remove chilled brownie from refrigerator, and place on top of ganache using an offset spatula to loosen, if necessary. Press gently to adhere. Transfer to refrigerator, and chill for 1 hour.
- 5. Remove from refrigerator, and trim edges. Cut into 2-by-2-inch squares. Store refrigerated in an airtight container for up to 1 week. Serve at room temperature.