Pin it
Peanut Butter M&M's Cake is the kind of dessert that gets quiet for a second when you set it down. The layers are soft and nutty, the candy gives little pockets of chocolate and crunch, and the frosting tastes like the inside of a peanut butter cup.
I like this as a birthday cake because it feels playful without needing complicated decorating. The main trick is simple. Chop the candy before it goes into the batter so it stays scattered through the cake instead of sinking in big pieces.
Peanut Butter M&M's Cake ingredients
This cake leans on creamy peanut butter, buttermilk, and chopped candy for its flavor and texture. Use a shelf-stable creamy peanut butter here, not the natural kind that separates, because it gives the batter a steadier structure.
- All-purpose flour. Gives the layers enough structure to hold the candy without becoming dense.
- Baking powder and baking soda. Lift the peanut butter batter and help it bake up soft.
- Unsalted butter. Adds richness and lets you control the salt.
- Creamy peanut butter. Brings the main flavor to both the cake and frosting.
- Granulated and brown sugar. Sweeten the cake while the brown sugar adds moisture.
- Eggs. Bind the batter and help the cake set. FoodSafety.gov advises cooking egg dishes fully and not tasting raw batter, which matters with cake batter too.
- Buttermilk. Keeps the crumb tender and balances the sweetness.
- Peanut Butter M&M's. Add color, chocolate, crunch, and extra peanut butter flavor.
- Powdered sugar and cream. Turn the peanut butter frosting smooth, fluffy, and spreadable.
Bake, cool, and frost
- Prepare the pans. Grease two 8-inch round cake pans, line the bottoms with parchment, and heat the oven to 350°F.
- Mix the dry ingredients. Whisk the flour, baking powder, baking soda, and salt. Toss the chopped candy with one spoonful of that flour mixture so it scatters better in the batter.
- Cream the base. Beat the butter, peanut butter, and sugars until lighter and creamy. This takes about 3 minutes and helps the cake bake with a softer crumb.
- Add eggs and vanilla. Beat in the eggs one at a time, then add the vanilla. Scrape the bowl so no thick peanut butter streaks stay at the bottom.
- Finish the batter. Add the dry ingredients in three additions, alternating with the buttermilk. Fold in the chopped candy gently.
- Bake the layers. Divide the batter between the pans and bake until the tops spring back and a tester comes out with a few moist crumbs, about 24-28 minutes.
- Make the frosting. Beat butter and peanut butter until smooth, then add powdered sugar, salt, vanilla, and cream until fluffy.
- Assemble the cake. Frost the cooled layers, add more candy on top, and chill briefly before slicing.
Keep the crumb tender
Peanut butter makes cake taste rich, but it can also make the crumb feel tight if the batter is overmixed. Once the flour goes in, mix only until you stop seeing dry streaks. A few small lumps are better than a tough layer. Buttermilk helps by adding moisture and a little acidity, so the cake stays softer after it cools.
Do not taste the batter, even if it smells good. The FoodSafety.gov egg safety guidance notes that raw eggs can carry Salmonella. Their raw flour guidance also explains that flour is not ready to eat until cooked.
Candy that stays scattered
Peanut Butter M&M's are heavier than mini chocolate chips, so I never fold them in whole for this cake. Rough chopping is enough. You want halves and chunky pieces, not candy dust. Tossing those pieces with a little flour from the recipe helps them cling to the batter.
Save the prettiest whole candies for the top. Press them into the frosting right after spreading it so they stick. If you are making this for a party, match the candy colors to the occasion or mix in a handful of chopped peanut butter cups for a richer topping.
Frosting without the slide
Peanut butter frosting can get heavy if it is packed with sugar and under-whipped. Beat the butter and peanut butter first until they look smooth and a little lighter, then add the powdered sugar gradually. Cream loosens the frosting, but add it slowly. You want soft swoops that hold their shape.
If your kitchen is warm, frost the first layer and chill it for 10 minutes before adding the second. That short rest firms the filling just enough to keep the top layer from drifting.
Make-ahead and storage
The layers can be baked a day ahead. Cool them completely, wrap them well, and keep them at room temperature. I prefer frosting the cake the day it will be served because the candy topping keeps its brighter crunch.
Once frosted, cover the cake and refrigerate it for up to 4 days. Because the frosting contains butter and cream, refrigeration is the better choice for longer storage. Bring slices back toward room temperature before serving so the frosting tastes creamy instead of firm.
Easy swaps for parties
This recipe works well in two 9-inch pans too, but the layers will be thinner and may bake a few minutes faster. For cupcakes, fill lined cups about two-thirds full and start checking around 17 minutes. The same frosting pipes nicely once it is beaten fluffy.
If peanut allergies are a concern, this is not the cake to adapt casually because peanut butter is built into the batter and frosting. For a chocolate candy cake instead, use a vanilla or chocolate base and regular candy-coated chocolates, then choose a frosting that matches your guests' needs.
Summary
Cool the cake layers completely before frosting, then chill the assembled cake for cleaner slices. Leftovers keep best covered in the refrigerator.
FAQs
- Can I use regular M&M's instead of Peanut Butter M&M's?
Yes. Regular M&M's work, but the cake will taste more like chocolate candy than peanut butter candy. If you still want a stronger peanut flavor, add two tablespoons of extra creamy peanut butter to the frosting.
- Why should I chop the M&M's first?
Whole candy pieces are heavy and can sink toward the bottom of the cake layers. Roughly chopping them gives you smaller bits that spread through the crumb and make cleaner slices.
- Can I make this cake ahead?
Yes. Bake the layers one day ahead, wrap them tightly, and keep them at room temperature. Frost the cake the next day, then chill it for 30 minutes before slicing if you want sharp edges.
- How should I store Peanut Butter M&M's Cake?
Store the frosted cake covered in the refrigerator for up to 4 days. Let slices sit at room temperature for 20-30 minutes before serving so the frosting softens.
- Can I bake this as a sheet cake?
Yes. Spread the batter in a greased 9x13-inch pan and bake at 350°F for about 30-35 minutes. Start checking early because glass, metal, and ceramic pans brown at different speeds.
- Can I freeze it?
You can freeze the unfrosted layers for up to 2 months. Wrap each cooled layer in plastic wrap and foil, then thaw overnight in the refrigerator before frosting.
