Step 1

Arrange a rack in the middle of the oven and heat the oven to 350°F. Coat an 8x8-inch baking pan with cooking spray, then line with parchment paper so that it hangs over two sides of the pan. Lightly coat the parchment with cooking spray.

Step 2

Coarsely chop 12 ounces of semi-sweet or bittersweet chocolate. Place in a medium microwave-safe bowl and add 1 stick unsalted butter. Microwave in 30-second intervals, stirring between each, until the mixture is melted and smooth, about 1 minute and 30 seconds total.

Step 3

Add 1/2 cup granulated sugar and 1/2 cup packed brown sugar, and whisk to combine. Add 2 large eggs and 1 teaspoon vanilla extract, and whisk to combine.

Step 4

Place 1 cup all-purpose flour, 2 tablespoons unsweetened cocoa powder, 2 tablespoons instant coffee or espresso powder, 1/2 teaspoon kosher salt, and 1/4 teaspoon baking powder in a small bowl and whisk to combine.

Step 5

Pour the flour mixture into the chocolate mixture and stir until just combined with no streaks of flour. Transfer the batter to the baking pan and spread into an even layer.

Step 6

Bake until a tester comes out with just a few crumbs, about 35 minutes. Let cool 1 hour before removing the brownie slab from the pan and cutting.