01 -
Preheat oven to 350°F. Line an 8x8 inch baking pan with parchment paper, leaving an overhang, or alternatively line with aluminum foil and lightly grease.
02 -
In a microwave-safe bowl, combine chopped dark chocolate, unsalted butter, and instant coffee powder. Microwave in 45-second intervals at medium power, stirring between each, until fully melted. Alternatively, melt together in a double boiler over low heat.
03 -
Allow chocolate mixture to cool slightly. Whisk in granulated sugar, beaten eggs, and vanilla extract until smooth.
04 -
Carefully fold in all-purpose flour and salt until just combined, taking care not to overmix.
05 -
Pour batter evenly into prepared pan. Bake for 23 to 28 minutes, until the top is set and a toothpick inserted in the center comes out clean or with a few moist crumbs.
06 -
Allow brownies to cool completely in the pan on a wire rack before frosting.
07 -
Dissolve instant coffee powder in boiling water. Cool completely, optionally refrigerate to speed cooling. In a large bowl, beat softened unsalted butter for 1 minute. Gradually add 1 cup powdered sugar, vanilla extract, and salt on low speed. Mix in cooled coffee mixture. Continue adding remaining powdered sugar in 1/2 cup increments until desired sweetness and consistency are reached. If needed, add 1 tablespoon whipping cream to adjust texture.
08 -
Using the parchment paper overhang, lift brownies from the pan and place on a cutting board. Spread buttercream evenly over the cooled brownies with a flat-edge knife. Slice into 12 portions with a sharp knife.