Pecan Fudge Brownies

Preheat oven to 350 degrees F. Butter an 8-inch-square baking pan. Line bottom with parchment paper, leaving an overhang on two sides. Butter paper; set pan aside. In a medium bowl, whisk together flour, baking powder, and salt; set aside. Place butter and chocolates in a large heatproof bowl set over (not in) a saucepan of simmering water. Heat until smooth, 2 to 3 minutes, stirring occasionally. Remove from heat, and stir in sugars, eggs, vanilla, flour mixture, and half of pecans. Transfer batter to prepared pan; smooth top. Sprinkle with remaining pecans. Bake until a toothpick inserted in center comes out clean, 30 to 35 minutes. Set pan on a wire rack; let cool completely. Using paper overhang, lift brownie onto a cutting board; cut into 16 squares. Store brownies in an airtight container at room temperature, up to 5 days.