Ingredients

1 cup (2 sticks) unsalted butter, cut into small pieces, plus more for pan 

1 cup all-purpose flour, plus more for pan 

10 ounces semisweet chocolate, coarsely chopped 

1 cup (about 4 1/2 ounces) malted-milk powder 

1 cup (about 4 ounces) malt balls, coarsely crushed 

1 1/2 cups packed light-brown sugar 

3 large eggs 

1 tablespoon pure vanilla extract 

Preparation

Preheat oven to 350 degrees. Butter and lightly flour a 9-by-13-inch baking pan; set aside.Combine chocolate and butter in a heatproof bowl set over simmering water; stir until melted and smooth. Set aside to cool slightly, about 5 minutes.

In a medium bowl, whisk together the flour, malted-milk powder, and malt balls; set aside. In the bowl of an electric mixer fitted with the whisk attachment, beat sugar and eggs until thickened and fluffy, about 2 minutes. Add melted chocolate mixture and vanilla; mix to combine, about 30 seconds more. Using a spatula, fold in flour mixture until just combined.

Pour batter into prepared pan, spreading it evenly with a rubber spatula. Bake until a cake tester inserted in the center comes out with just a few crumbs on it, 30 to 35 minutes. Transfer brownies to a wire rack to cool.