Peanut Butter Brownie Frosting (6 Ingredients)

Take your peanut butter and chocolate pairing to the next level with this decadent 6 ingredient peanut butter brownie frosting. In just 15 minutes, you’ll enjoy a frosting that makes even the best brownies better.  

If you want to add extra decadence and elegance to your basic brownies, this six ingredient peanut butter brownie frosting recipe suits your needs. Easy to whip up, this buttercream frosting comes together in just 15 minutes and only requires one bowl to make. 

Filled with richness and a lovely light texture, it's the perfect pairing for a dense, fudgy brownie. 

• My secret to a light and fluffy brownie frosting.
• The best type of peanut butter to use for peanut butter brownie frosting.
• Storage instructions in case you want to make the peanut butter buttercream ahead of time. 

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Unsalted butter: For the best frosting, allow the butter to soften to room temperature. The butter should slightly give when you push against it but overall still hold its form. If you’re opting to use salted butter, be sure to adjust the amount of extra salt added to the recipe.  

Peanut butter: The best peanut butter for this recipe is a nice creamy one. I would avoid using any “natural” peanut butter because these tend to have separated oil. This oil could damage the consistency of the buttercream frosting by making it too oily.

Confectioners’ sugar: Otherwise known as powdered sugar or icing sugar, this ingredient sweetens the frosting and also is responsible for adding structure. Be sure to measure first, then sift the confectioners’ sugar to achieve the best consistency. 

Heavy cream: This ingredient helps thin out the buttercream icing, making it spread much easier. For the longest shelf life on your frosting, use very fresh heavy cream. Always checking the expiration date on the heavy cream will allow your buttercream to last up to one month after preparing it. 

Vanilla extract: Vanilla extract adds another level of flavor to the peanut butter frosting. With vanilla extract, I recommend paying a bit extra for a high-quality product such as Rodelle. 

Fine sea salt: Salt both enhances the other flavors and helps balance out the overall sweetness of the icing. 

1. To begin making the peanut butter brownie frosting, add the butter and peanut butter into the bowl of a stand mixer fitted with a paddle attachment. Turn the mixer on medium-high speed and let it beat these ingredients for 2 to 3 minutes until it's light and fluffy. 

Using a silicone spatula, be sure to scrape the sides of the mixer bowl to ensure all the butter and peanut butter is evenly mixed.

2. Next, reduce the speed on the stand mixer to medium-low and add in the confectioners’ sugar. Remember to sift the confectioners’ sugar before adding it to the butter mixture. This will prevent any clumps from forming and ruining the light and smooth texture of the frosting.

With a thick paste formed, it is time to thin out the frosting by adding in the heavy cream. At this point, go ahead and add the vanilla extract and fine sea salt as well.

3. For the best textured frosting, crank the speed on the stand mixer back up to medium-high and allow the buttercream frosting to beat for an additional 5 minutes.

After five minutes, the frosting should be light and fluffy. Don't be tempted to cut this time short! 

4. Lastly, using an offset spatula, evenly spread the frosting across a 9 x 9 inch pan of brownies. The offset spatula will allow you to form a lovely wavy pattern on the top of the brownies. 

For a smooth look to the frosting, fill a glass of hot water and dip the offset spatula in for a few seconds. Remove the spatula and shake off any excess water.

Then, slowly run the spatula along the top of the frosting to make as smooth of a layer as possible.