Lining the pan isn't busywork; it makes it easy to remove the brownies.
- 8 tablespoons (1 stick) unsalted butter, cut into pieces, plus more for pan
- 1 cup all-purpose flour (spooned and leveled)
- 1/4 cup unsweetened cocoa powder
- 1/2 teaspoon baking powder
- 1/2 teaspoon salt
- 8 ounces semisweet or bittersweet chocolate, chopped
- 1 1/4 cups sugar
- 3 large eggs
Preheat oven to 350 degrees. Brush a 9-inch square baking pan with butter. Line bottom and two sides with a strip of parchment paper, leaving a 2-inch overhang on the two sides. Butter paper, and set pan aside. In a small bowl, whisk flour, cocoa, baking powder, and salt; set aside.
Place butter and chocolate in a large heatproof bowl set over (not in) a saucepan of gently simmering water. Heat, stirring occasionally, until smooth, 2 to 3 minutes; remove bowl from pan. Add sugar; mix to combine. Add eggs, and mix to combine. Add flour mixture; mix just until moistened (do not overmix). Transfer batter to prepared pan; smooth top.
Bake until a toothpick inserted in center comes out with a few moist crumbs attached, 50 to 60 minutes. Cool in pan for 30 minutes. Using paper overhang, lift brownies out of pan; transfer to a rack to cool completely (still on paper). On a cutting board, using a dampened serrated knife, cut into 16 squares.