Active Time

　　15 min

　　Total Time

　　1 1/4 hr

　　

Ingredients

Makes 32 (2-inch) squares

　　2 sticks (1/2 pound) unsalted butter

　　8 ounces fine-quality bittersweet chocolate (no more than 60% cacao if marked)

　　2 cups sugar

　　1 teaspoon pure vanilla extract

　　5 large eggs

　　2/3 cup all-purpose flour

　　1/3 cup unsweetened Dutch-process cocoa powder

　　1/2 teaspoon salt

　　

Step 1

Preheat oven to 350°F with rack in middle. Butter and flour a 13- by 9-inch baking pan.

　　

Step 2

Melt butter and chocolate in a 3-qt heavy saucepan over low heat, stirring, until smooth. Remove from heat and cool to lukewarm. Whisk in sugar and vanilla. Whisk in eggs 1 at a time until mixture is glossy and smooth.

　　

Step 3

Whisk together flour, cocoa powder, and salt, then whisk into chocolate mixture until combined.

　　

Step 4

Spread in pan and bake until a pick inserted in center comes out with crumbs, 25 to 35 minutes. Cool completely.