Old-Fashioned Peanut Butter Icing

Transform an ordinary yellow cake with this delicious sweet and nutty old-fashioned peanut butter icing recipe. It’s a must-make for peanut butter fans!

Today, I’m sharing a recipe with a big old root system behind it: yellow cake with old-fashioned peanut butter icing. The cake we’re going to use is just a boxed mix because spoiler: it’s not the cake that is important here, it’s the icing. This is my grandmother’s old-fashioned peanut butter icing recipe to be exact and it will forever remind me of my great aunt, Red.

Now, most old-fashioned icing recipes are of the boiled icing variety. If this technique scares you, don’t worry, I’ve included lots of tips for success below to make sure you nail it every time. Trust me, when you get it right and give it a taste, you’ll want to make it again and again. Who can resist a thick layer of sweet yet nutty peanut butter icing on their favorite cake? Certainly not me! The best part of boiled icing is that you pour the hot icing onto the cooled cake and it hardens like fudge… YUM!

To make my peanut butter frosting, you’ll need creamy peanut butter (of course), as well as icing essentials like granulated sugar, vanilla, milk, shortening, and butter. So grab those ingredients and get ready, because I just know you’re going to love this old-fashioned peanut butter icing recipe as much as I do!

Recipe Ingredients

• Sugar
• Shortening (I use coconut oil these days)
• Peanut butter
• Milk
• Vanilla extract 
• Unsalted butter

How To Make Old-Fashioned Peanut Butter Icing

In a large saucepot, combine sugar, milk, shortening, margarine, and salt.

Bring to a rolling boil over medium-high heat, stirring constantly to prevent scorching.

Once it reaches a boil, let it boil for two to three minutes without stirring.

Remove from heat and immediately stir in the vanilla and peanut butter.

Beat until icing is smooth and starts to lose its shine. 

Immediately pour it onto the baked and cooled cake. 

Allow it to cool before serving.

Look at that nice layer of peanut butter fudge icing! 

Can you see why yellow cake with old-fashioned peanut butter icing is such a special cake? 

This is a sight to behold.

Guess what? It seems like it was a gift from above, but as a precious reminder of my past and its connection to the future, this is my daughter’s favorite cake. 

Now excuse me while I dig into this delicious slice of yellow cake!

Storage

Store leftover cake in an airtight container in the fridge for up to 1 week.

Recipe Notes

Here are my tips for success when it comes to boiled peanut butter icing:

• • The boiling of the icing is the most critical step. Make sure it comes to a rolling boil and then stay right there, timing it. I suggest adding one minute to be on the safe side but don’t go over this as the icing will scorch. 
  • You absolutely must have your cake done and ready the moment the icing is done. 
  • Once your icing is finished, remove it from the heat and use a wire whisk to quickly stir in the peanut butter and vanilla until the icing thickens a bit and starts to lose some of its shine. It should still be pourable. 
  • Don’t try to spread the icing once you’ve poured it. Instead, pour it evenly over the cake so that no spreading is needed.
  • Most importantly, unless you lived through the Great Depression, I strongly encourage you not to use this on anything other than a sheet cake. Only those who have the crown of wisdom that comes through age and hardship can ice a layer cake with this. 
• If you want more peanut butter flavor, sprinkle the cake with roasted peanuts or crushed nuts.
• Natural peanut butter doesn’t work as well as regular peanut butter in this recipe.
• For creamier icing, you can substitute the milk for buttermilk.

Recipe FAQs

What other cakes work well with old-fashioned peanut butter icing?

You can use any kind of boxed cake mixes, such as vanilla cake, angel food cake, golden cake, white cake, or even chocolate cake (which will suit Reese’s Peanut Butter Cup fans). But if you’re looking for a homemade cake recipe, Aunt Sue’s easy pound cake would be perfect with this peanut butter icing.

Check out these other irresistible icing recipes:

Boiled Chocolate Icing

Italian Cream Cake with Pecan Cream Cheese Icing

7-Minute Frosting (Foolproof Recipe)

Vegan Sweet Potato Cake With Maple Cashew Icing

Creamy Chocolate Frosting

Cappuccino Cake With Cappuccino Buttercream Frosting

This post was originally published in July of 2008. I updated the photos in August 2019.