BIG-BATCH TRIPLE-CHOCOLATE BROWNIE BARS

Big-Batch Triple-Chocolate Brownie Bars image

Provided by Martha Stewart

Time 1h5m

Yield Makes 54

Number Of Ingredients 13

3 sticks unsalted butter, cubed, plus more, softened, for sheet
3 cups unbleached all-purpose flour
1/4 cup Dutch-process cocoa powder
1 1/2 teaspoons baking soda
1 1/2 teaspoons kosher salt
1 pound bittersweet chocolate, coarsely chopped (3 cups)
1 cup granulated sugar
1 1/2 cups packed light-brown sugar
3 large eggs, room temperature
2 teaspoons pure vanilla extract
8 ounces roasted unsalted nuts, such as peanuts, pecans, or walnuts, coarsely chopped (1 2/3 cups)
6 ounces dried fruits, such as raisins, currants, or cherries (1 1/4 cups)
4 ounces white chocolate, coarsely chopped (3/4 cup)

Steps:

Preheat oven to 350 degrees. Brush a 13-by-18-inch rimmed baking sheet with butter. In a bowl, whisk together flour, cocoa, baking soda, and salt until thoroughly combined.
In a large heatproof bowl set over a pot of simmering water, melt butter with 10 ounces (2 cups) bittersweet chocolate. Remove from heat; stir until smooth. Let cool 5 minutes. Add both sugars, eggs, and vanilla and beat on medium speed, or whisk vigorously by hand, until thickened slightly and glossy, 2 to 3 minutes. Reduce speed to low; beat in flour mixture just until combined. Stir in two-thirds of nuts and dried fruits.
Transfer batter to prepared sheet, spreading evenly to edges. Sprinkle evenly with white chocolate and remaining nuts, dried fruits, and 1 cup bittersweet chocolate. Gently press toppings into batter with flattened palms.
Bake until edges are puffed and just set but center is still wobbly, 20 to 23 minutes. Transfer pan to a wire rack; let cool completely. Cut lengthwise into thirds, then crosswise into 1-inch-thick rectangles. Bars can be stored in an airtight container at room temperature up to 5 days, or stacked between layers of parchment in a freezer bag and frozen up to 1 month. (Thaw at room temperature before serving.)