Introduction

These Dark Chocolate Guinness Brownies with Buttercream are rich, fudgy, and full of deep flavors. The Guinness reduction adds a subtle malty note that perfectly complements the dark chocolate. Topped with a smooth espresso buttercream, they make an indulgent treat for any occasion.

A square piece of chocolate cake sits on a small white plate with a slightly speckled texture; the cake has two layers with a moist, dark brown bottom layer and a thick top layer of light brown frosting with visible specks and a creamy but slightly textured surface. The cake has a small bite taken out of one corner, showing the softness and crumbly texture inside. In the blurred background, another piece of the same cake is seen resting on a white plate against a soft white marbled texture surface. Photo taken with an iphone --ar 4:5 --v 7

Ingredients

½ cup unsalted butter
6 ounces dark (baker’s) chocolate (2 bars)
1 ½ cups granulated sugar
12 ounces Guinness beer (1 bottle or can)
1 teaspoon vanilla extract
3 eggs
½ teaspoon espresso powder
1 cup all-purpose flour
½ cup softened butter (for buttercream)
2 cups powdered sugar
½ teaspoon espresso powder (for buttercream)

Instructions

Step 1: Preheat your oven to 350°F (175°C). Grease and flour a 9×9-inch baking dish to prevent sticking.
Step 2: Pour the Guinness into a saucepan over high heat. Boil and reduce until about ⅔ cup remains, which takes around 10–12 minutes. Transfer the reduction to a heat-safe measuring cup and let it cool for at least 15 minutes.
Step 3: While the Guinness reduces, melt the dark chocolate and ½ cup unsalted butter in a medium microwave-safe bowl. Heat in 30-second intervals, stirring between each, until smooth and fully melted.
Step 4: Stir granulated sugar into the melted chocolate mixture, then add the eggs, vanilla, and ½ cup of the cooled Guinness reduction. Mix until combined.
Step 5: Add salt and flour, stirring gently until just incorporated. Be careful not to overmix; the batter should be thick and fudgy.
Step 6: Pour the batter into your prepared baking dish and bake for 30–35 minutes. Test doneness with a toothpick—it should come out with moist crumbs but no wet batter. If needed, bake in 3-minute increments until done.
Step 7: Let the brownies cool completely on a wire rack for at least 2 hours before frosting.
Step 8: For the buttercream, beat ½ cup softened butter until smooth and creamy using a stand or hand mixer. Gradually add powdered sugar and ½ teaspoon espresso powder, mixing until the texture is thick and dense.
Step 9: Add the remaining Guinness reduction to the buttercream a tablespoon at a time, beating until the frosting becomes light and fluffy.
Step 10: Spread the buttercream evenly over the cooled brownies and cut into squares to serve.

Tips & Variations

For an extra espresso kick, sprinkle a little instant coffee over the frosting before serving.
If you prefer a less intense beer flavor, reduce the amount of Guinness reduction used in the batter.
Use good quality dark chocolate for the best rich flavor and texture.
To keep brownies extra fudgy, slightly underbake and let them finish cooking as they cool.

Storage

Store the frosted brownies in an airtight container at room temperature for up to 3 days. For longer storage, refrigerate them for up to a week; bring to room temperature before serving for the best texture. You can also freeze unfrosted brownies for up to 2 months and frost them after thawing.

How to Serve

A close-up image of a single square piece of rich, dark brown chocolate brownie with a smooth, shiny light caramel-colored frosting layer on top, about one layer thick, showing a slightly swirled texture. The brownie looks moist and dense with a crumbly texture at the sides. The background is a white marbled texture beneath the brownie with some scattered crumbs, and a blurred larger piece of the same brownie is visible behind it. Photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I use a different type of beer instead of Guinness?

Yes, you can use other dark beers like stouts or porters to achieve a similar flavor profile. Avoid light beers as they won’t provide the same depth.

What if I don’t have espresso powder?

If you don’t have espresso powder, you can substitute with a small amount of instant coffee granules or omit it entirely; the brownies will still be delicious but with less coffee undertone.