Brownie Frosting Recipe

This brownie frosting recipe is a thick, glossy chocolate frosting made with ½ cup butter, ⅓ cup cocoa powder, 2 cups powdered sugar, and ¼ cup milk or cream. It takes 10 minutes with a hand mixer, makes about 1½ cups, and covers one 9×13 inch pan of brownies, then sets to a soft, fudge-like finish in about an hour.

The trick is adding the sugar slowly. It goes in ½ cup at a time with a tablespoon of milk after each addition, so the frosting stays smooth instead of gritty or stiff. After years of baking, this is the chocolate frosting for brownies I come back to, whether the base is from scratch or a boxed mix.

Brownie Frosting Quick Facts

• Time: 10 minutes, no cooking
• Yield: about 1½ cups, enough for one 9×13 inch pan of brownies
• Main ratio: 2 cups powdered sugar to ½ cup butter and ⅓ cup cocoa
• Liquid: ¼ cup whole milk or heavy cream, added 1 tablespoon at a time
• Set time: at least 1 hour on cooled brownies before slicing
• Storage: 5 days in the fridge, 2 months in the freezer

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Best Frosting for Brownies: Chocolate Fudge vs Buttercream vs Ganache

Three toppings come up whenever people look for the best frosting for brownies. Here is how they compare on the things that matter for a pan of bars.

• Chocolate fudge frosting (this recipe): sets soft in about an hour, medium sweet with a strong cocoa flavor, and slices cleanly once set, especially after a short chill. It spreads in thick swirls and stays creamy. A cooked version like my chocolate fudge frosting is another good fudge frosting for brownies.
• Buttercream: stays soft and never fully sets, and it is the sweetest of the three because it uses more sugar. It pipes well, but on brownies it can smear when you cut. A classic American buttercream or a chocolate buttercream frosting is better for cakes and cupcakes.
• Ganache: made from just chocolate and cream, so it is the least sweet. It needs longer to firm up, usually an hour or more at room temperature, and it slices very cleanly once firm. My chocolate ganache frosting gives a shiny, smooth top.

For most pans I choose the fudge style. It is faster than ganache, less sugary than buttercream, and it uses pantry staples. If you want icing for brownies that hardens to a firm top, ganache is the better pick.

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What Goes Into This Chocolate Frosting for Brownies

Only six ingredients, and each one has a job.

• Unsalted butter (½ cup): softened to room temperature so it whips light. Unsalted lets you control the salt.
• Cocoa powder (⅓ cup): sifted to remove clumps. Dutch-process gives a darker, richer look, while natural cocoa tastes brighter. Both work.
• Powdered sugar (2 cups): sifted too, so the icing is never grainy. It sweetens and thickens at the same time.
• Whole milk or heavy cream (¼ cup): milk keeps it lighter, cream makes it richer and a little thicker.
• Vanilla (1 teaspoon) and a pinch of salt: round out the chocolate and keep the sweetness in check.

This frosting sits softer than buttercream and spreads more like a chocolate pudding frosting. For a deeper, less sweet flavor with the same buttery body, a dark chocolate buttercream is a good cousin.

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How to Make Brownie Frosting in 10 Minutes

Beat the softened butter on medium speed for 2 to 3 minutes, until it turns lighter in color and fluffy. The butter should be soft but not melting. This step adds air and gives the frosting its body.

Sift the cocoa powder straight into the bowl and mix on low until it disappears. The mixture looks thick and dark at this point, which is normal.

Add the powdered sugar ½ cup at a time, with 1 tablespoon of milk or cream after each addition, and beat well in between. Finish with the vanilla and salt. If it feels too thick, add more milk 1 teaspoon at a time. If it is too thin, beat in a little more powdered sugar. Taste it at the end; I sometimes add an extra pinch of salt when the sugar feels strong.

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Frosting a 9×13 Pan of Brownies

Let the brownies cool completely first. On a warm base the frosting melts and slides. I once rushed this step and ended up with a streaky top, so now I always wait.

Drop all the frosting in the center and spread it outward with an offset spatula or butter knife, using a light hand. Drag the spatula across the top for swirls. It works on dense classic fudgy brownies, cocoa powder brownies, boxed mixes, and a chocolate sheet cake. Give it at least an hour to set before cutting.

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Brownie Frosting Mistakes and Fixes

• Grainy icing: the sugar or cocoa was not sifted. Sift both, and beat for another minute.
• Too stiff to spread: add milk 1 teaspoon at a time until it moves easily.
• Runny or sliding off: the butter was too warm or the brownies were still warm. Chill the frosting for 10 to 15 minutes, cool the pan fully, and try again.
• Too sweet: use heavy cream instead of milk and add a pinch more salt.
• Messy slices: the topping had not set. Wait at least an hour, or chill the pan briefly, and wipe the knife between cuts.

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How Long It Keeps

Store leftover frosting in a covered container in the fridge for up to 5 days. Bring it back to room temperature and stir before using. To freeze, press it flat in a freezer bag and keep it for up to 2 months, then thaw overnight in the fridge and re-whip.

Frosted brownies cut neatly once the top has set. I like them slightly chilled, which gives the frosting a firm bite while the center stays soft. For parties, finish them with sprinkles, a dusting of cocoa, or a drizzle of melted chocolate.

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Icing for Brownies: Quick Answers

Do you frost brownies warm or cold?

Frost brownies once they are completely cool. Warm brownies melt this frosting so it slides and turns streaky.

How much frosting for a 9×13 pan?

About 1½ cups, which is one batch of this recipe (½ cup butter, 2 cups powdered sugar, ⅓ cup cocoa, and ¼ cup milk). That gives a thick, even layer over one 9×13 inch pan.

What is the best frosting for brownies?

A chocolate fudge frosting like this one is the best all-round choice: quick, not overly sweet, and it slices cleanly once set. Choose ganache for a firmer, less sweet top.

Is brownie frosting the same as icing for brownies?

Yes, people use both words for the same thing. This recipe is a thick, spreadable icing rather than a thin glaze.

Does this brownie frosting harden?

It sets to a soft, fudge-like layer and firms up more in the fridge, but it does not dry hard. For a harder top, use ganache.

Can I use this frosting on other desserts?

Yes. It works on a Texas sheet cake style bake, cookies, or ice cream sandwiches. For a lighter, fluffier topping, try whipped chocolate frosting.

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Before You Bake

If you came looking for the best brownie frosting recipe for an everyday pan, this is the one I would start with. Soften the butter, sift the cocoa and sugar, and let your brownies cool while you mix. If you like richer toppings, German chocolate frosting with coconut and pecans is another favorite. Tell me in the comments how your pan turned out.