Instructions

• Preheat the oven to 350°F. Spray a 9x13-inch pan with nonstick spray, then line the pan with parchment paper leaving an overhang on the long sides to lift the brownies out later.
• Place the 1 cup (2 sticks) unsalted butter, 8 ounces coarsely chopped semi‑sweet chocolate, and 3 ounces coarsely chopped unsweetened chocolate in a small saucepan. Melt over the lowest possible heat, stirring constantly, until smooth, about 3–5 minutes. Remove from heat and let the chocolate mixture cool until it is no longer hot (warm or room temperature).
• In a large mixing bowl, whisk together 1 cup + 2 tablespoons granulated sugar, 3 large eggs (at room temperature), and 1 tablespoon vanilla extract until combined.
• Add the cooled chocolate‑butter mixture to the sugar‑egg mixture and whisk until just combined.
• In a separate bowl, stir together 3/4 cup all‑purpose flour, 1 1/2 teaspoons baking powder, and 1/2 teaspoon kosher salt. Stir the dry ingredients into the wet ingredients until no white streaks of flour remain.
• Scrape the batter into the prepared pan and smooth the top with a spatula. Evenly sprinkle 1 cup (or more) coarsely chopped walnuts (or pecans) and 1 cup semi‑sweet chocolate chips over the batter. Gently press the nuts and chips into the batter so they adhere.
• Bake in the preheated oven for 30–35 minutes, until a toothpick inserted into the center comes out clean or with just a few moist crumbs.
• Remove the pan from the oven and let the brownies cool completely in the pan on a wire rack. Once cooled, cover and refrigerate if you prefer firmer brownies. Use the parchment overhang to lift the brownie slab from the pan and cut into 24 squares.