Brownies With Frosting Recipe

Prepare oven and pan

Preheat the oven to 350°F (175°C). Line an 8x8-inch (20x20 cm) baking pan with parchment paper leaving a 1-inch overhang, or lightly grease the pan with butter or cooking spray.

Melt chocolate and butter

Place the chopped bittersweet chocolate and 1 cup unsalted butter in a heatproof bowl set over a pot of simmering water (double boiler) or microwave in 20–30 second intervals, stirring between bursts, until smooth. Remove from heat and let cool 3–5 minutes.

Combine sugars and eggs

In a large bowl, whisk together 1 1/2 cups granulated sugar and 1/4 cup packed light brown sugar. Add the eggs one at a time, whisking vigorously after each addition until fully incorporated. Whisk in 2 teaspoons vanilla extract.

Incorporate chocolate into egg mixture

Pour the slightly cooled melted chocolate-butter mixture into the sugar-egg mixture and whisk until homogeneous and glossy.

Dry ingredients

Sift together 1 cup all-purpose flour, 1/2 cup unsweetened cocoa powder, 1/2 teaspoon kosher salt, and 1/4 teaspoon baking powder into a medium bowl to remove lumps.

Combine wet and dry

Fold the dry ingredients into the chocolate-egg mixture using a rubber spatula until just combined. Do not overmix. If using, fold in 1/2 cup chocolate chips or chopped nuts now.

Bake

Pour batter into the prepared 8x8 pan and smooth the top with an offset spatula. Bake in the preheated oven for 25–30 minutes, or until the edges are set and a toothpick inserted into the center comes out with a few moist crumbs (not wet batter). Rotate the pan halfway through baking for even browning.

Cool before frosting

Remove brownies from oven and place on a wire rack. Let the brownies cool in the pan for 20–30 minutes, then use the parchment overhang to lift them out and cool completely on the rack (about 45–60 minutes total) before applying frosting so it doesn't melt.

Prepare frosting

With the brownies cooling, make the frosting. In a medium bowl, beat 1/2 cup softened unsalted butter with an electric mixer on medium speed until creamy (about 1 minute). Add 3/4 cup unsweetened cocoa powder and 2 cups powdered sugar alternately with 3 tablespoons whole milk, starting and ending with the powdered sugar. Beat until smooth and spreadable, about 2–3 minutes. Add 1 teaspoon vanilla extract and 1/8 teaspoon salt; beat another 15–20 seconds. If frosting is too thick, add additional milk 1/2 tablespoon at a time; if too thin, add 1–2 tablespoons more powdered sugar.

Frost the brownies

When brownies are completely cool, transfer them back to the baking pan or place on a cutting board. Use an offset spatula or butter knife to spread the frosting evenly over the top, working from the center toward the edges. Smooth or create swirls as desired.

Set and slice

Allow the frosting to set at room temperature for at least 30 minutes, or chill 15 minutes in the refrigerator for a firmer set. For clean slices, run a sharp knife under hot water, dry it, then make straight cuts; wipe the knife between cuts. Cut into 9 (3x3) or 12 (3x4) squares.

Serve brownies at room temperature. Store leftover brownies in an airtight container at room temperature for up to 3 days or refrigerated for up to 7 days. If refrigerated, bring to room temperature before serving for best texture. You may also freeze unfrosted brownies for up to 3 months; thaw and then frost.