Ingredients
nonstick cooking spray1cup unsalted butter6ounces unsweetened chocolate, finely chopped2ounces bittersweet chocolate, finely chopped1tablespoon cocoa powder4large eggs, room temperature1large egg yolk, room temperature3cups packed light brown sugar2teaspoons instant espresso powder2teaspoons pure vanilla extract¾cup unbleached, all-purpose flour¼cup cake flour, not self-rising1teaspoon sea salt¾cup bittersweet chocolate chips
Preparation
Preheat oven to 375°F. Coat a 13x9-inch baking pan with nonstick cooking spray; line with parchment or aluminum foil. Reserve. Add the butter and chocolates to a heatproof bowl and place over a pot of simmering water. Once both are completely melted, stir in the cocoa powder and set aside to cool to room temperature. Reserve. Put the eggs and yolk in a medium-large mixing bowl. Insert the mixing beaters into the Cuisinart® Hand Mixer. Mix the eggs and egg yolk on speed 4 until lightened, about 30 seconds. Add the brown sugar and beat on speeds 5 to 6 until light and thickened, another 1 to 2 minutes. Add instant espresso and vanilla; beat until well combined. Stir the flours and salt together and then into the chocolate mixture. Add the chocolate/flour mixture to the egg/sugars mixture and mix on speed 1 until just incorporated. With the mixer running, add the chocolate chips. Pour into prepared pan. Bake for about 45 to 50 minutes, or until edges are dry. Cool completely before cutting.
