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Toasted Marshmallow Special K-Bars – a sweet, salty, peanutty, and just slightly toasty chocolate treat that’s impossible not to love. These bars are made with creamy peanut butter, salted butter, toasted marshmallows, and topped with rich chocolate. They’re chewy, gooey, a little nostalgic, and totally addictive. Whether you’re making them for a summer dessert, school bake sale, or just because—it’s a guaranteed crowd-pleaser.
Oh, how I adore this recipe! My mom is known for a handful of classic desserts—her oatmeal chocolate chip cookies, death by chocolate cake, and of course, her famous Special K-Bars. I don’t know if K-Bars are a strictly Midwest thing, or where the original recipe even came from, but growing up, no one made them quite like my mom. She just had that magic touch.
Her recipe was simple and very old-school: 1 cup creamy peanut butter, 1 cup Karo syrup, and 1 cup sugar, melted together and mixed with cornflakes. She’d press it into a pan, melt a good amount of semi-sweet chocolate chips for the topping, and that was it. Classic. And so good! Any time she made them, they disappeared within a day—everyone loved them.
Today, I’m giving her classic bars a little twist by adding toasted marshmallows. Think of it as a mash-up between a marshmallow treat and a K-bar—chewy, chocolatey, and just a little gooey in the best way. They’re fun to make (no matter your age!) and even more fun to eat.
Let’s dive into the details
Ingredients
- mini marshmallows
- salted butter
- creamy peanut butter
- cornflakes
- regular marshmallows
- semi-sweet chocolate chips
Special Tools
You’ll need to use your oven’s broiler for this recipe. You’ll also need a large pot, sheet pan, and a 9×13 pan.
Steps
Step 1: Make the Peanut Butter Mixture
In the largest pot you have, melt salted butter with creamy peanut butter over medium heat. Stir frequently and bring the mixture to a gentle boil—this should take about 5 minutes. The mixture should be smooth and fully combined.
If you like, add a pinch of flaky sea salt for a little extra flavor.
Step 2: Add Marshmallows and Cereal
Once the peanut butter mixture is smooth, stir in the mini marshmallows until completely melted and gooey.
Then, mix in the cornflake cereal. Stir until the cereal is well coated in the peanut butter-marshmallow mixture.
Step 3: Toast the Marshmallows
To get that toasted marshmallow flavor, arrange a layer of mini marshmallows on a baking sheet and broil until golden and lightly charred.
Important: Don’t walk away while these toast! Every broiler is different, and marshmallows can go from perfectly golden to burnt in seconds. Watch them closely.
Once toasted, gently fold the marshmallows into the cereal mixture. No need to overmix—swirls and pockets of toasted marshmallow are exactly what you want.
Step 4: Press and Top with Chocolate
Line a baking pan with parchment paper and press the cereal mixture firmly into the pan.
Melt the chocolate chips until smooth, then pour the melted chocolate over the bars and spread it out evenly.
Refrigerate the bars until set—about 2 hours. Once firm, cut them into squares or bars.
They’ll be a little gooey, a little messy, and totally irresistible. Perfect for backyard BBQs, picnics, or just a fun summer dessert!
Looking for easy party summer desserts? Here are a few ideas:
Chewy Chocolate Peanut Butter Bars
Chocolate Peanut Butter Pretzel Blondies
Homemade Vegan Peanut Butter Twix Bars
Caramel Butter Cake with Fudgy Chocolate Frosting
Retro-Style Chocolate Sheet Cake
Lastly, if you make these Toasted Marshmallow K-Bars, be sure to leave a comment and/or give this recipe a rating! Above all, I love hearing from you and always do my best to respond to each and every comment. And, of course, if you make this recipe, don’t forget to tag me on Instagram! Looking through the photos of recipes you all have made is my favorite!
Toasted Marshmallow K-Bars
Servings: 24 bars
Calories Per Serving: 268 kcal
Nutritional information is only an estimate. The accuracy of the nutritional information for any recipe on this site is not guaranteed.
Ingredients
- 1/2 cup (1 stick) salted butter, at room temperature
- 1 bag (10 ounce) mini marshmallows
- 1 cup creamy peanut butter
- 5 cups Corn Flakes or Rice Krispies cereal
- 2 cups regular marshmallows
- 20 ounces semi-sweet/dark chocolate, melted
- flaky sea salt (optional)
Instructions
- 1. Line a 9×13 inch pan with parchment paper. Preheat the broiler.2. Add the butter and peanut butter to a large pot set over medium heat. Let the butter melt into the peanut butter. Turn the heat to low. Add the mini marshmallows and stir until melted, about 5 minutes. Remove from the heat.3. Mix in the cereal. 4. Arrange the regular marshmallows on a baking sheet. Broil 1-2 minutes, until toasted. Watch closely, the marshmallows will toast FAST. Mix the toasted marshmallows into the cereal. Immediately transfer the mixture to the prepared pan, spreading it evenly and packing it in tightly. 5. Pour over the chocolate. Sprinkle with sea salt (if desired).6. Chill in the fridge until firm, at least 1-2 hours. Cut into bars. Enjoy!
This post was originally published on June 24, 2025
I made these for Independence Day for my family. They were amazing!
Love to hear this, Karen! Thanks so much for choosing to make this recipe for the 4th! Have a wonderful weekend!
Wow!! Another over the top recipe. Easy & delicious. Thank you for making cooking such fun!!
Hey Susan,
Fantastic!! So glad to hear you enjoyed this recipe, thanks a bunch for giving it a try!
Unreal! My girlfriend and I made these last night, and we can’t stop eating them. We used unsalted butter and they turned out amazing!
Hey Adam,
Happy Tuesday!! I’m so glad to hear this recipe turned out nicely for you, thanks a lot for making it!
Made these with my kids today as written. We used corn flakes. They were so easy and delicious! A new summer treat ❤️
Hey Karen,
Happy Tuesday!! I’m so glad to hear this recipe turned out nicely for you, thanks a lot for making it!
Bars are just cooling!! Optimistic they turned out- just not sure there as thick as yours!!
Hey Linda! Yay, I hope you love them! Let me know what you think! 🙂 xT
Hi!! We just made these and they’re SO yummy!! I know you chill them for 1-2 hours but how do you recommend storing them? Refrigerator or at room temp? Thanks so much!!
Hey Katherine,
I appreciate you giving this recipe a try, so glad to hear it turned out nicely for you! If your kitchen is on the warmer side, I would keep them in the fridge. Have a great summer weekend!
I made these last night, and they were a hit!
Hey Karin,
I appreciate you giving this recipe a try, so glad to hear it turned out nicely for you! Have a great summer weekend!
Hi,
If not eating until tomorrow do I leave them in the refrigerator or just two hours and leave them out?
Thanks,
Angela
Hi Angela,
I would keep them in the fridge especially if the temps are warmer where you live:) I hope you love this recipe!
Hi do you melt the chocolate?
Hi Zoey,
I just melt my chocolate in the microwave and check it every 10 seconds or so. Please let me know if you have any other questions!
I left out the peanut butter and it didn’t work. Any suggestions/insight?
Hi Brenda,
Sorry to hear this. What didn’t work? Can you elaborate on what went wrong so I can better help? Thanks!
The bars didn’t hold together at all. Was this tested without peanut butter?
Hey Brenda,
So sorry to hear this. Without the peanut butter it’s just a basic Rice Krispie treat recipe.
Growing up in central MN, these were at every picnic. We made them with Rice Krispies and still called them Special K bars. Or mixed in a bunch of butterscotch chips and called them Scotcheroos.
Love this, Liz!! Thanks so much for sharing:) I hope you love this recipe just as much as your own!
Isn’t one of the ingredients of K bars…special k? How are these k bars?
Hi Tracie,
My mom always made them with corn flakes, but you could totally use special K! Please let me know if you give this recipe a try, I hope you love it!
How many extra mini marshmallows do you think that I would need to use to omit the peanut butter?
Hi Rebecca,
No need to add more marshmallows, you can just omit the peanut butter. I hope this helps! Please let me know if you give this recipe a try!
We can leave out a whole cup of peanut butter and it won’t affect the recipe? Is this correct?
Yes:)
In step 1 you have melt 1 ½ sticks of salted butter but in the list of ingredients, you have 1/2 cup (1 stick) listed. Just checking which one is correct. Thank you. Can’t wait to make them
Hi Penny,
You will want to use 1 stick of butter for this recipe:) Please let me know if you have any other questions!
your explanation calls for 1 and 1/2 sticks of butter. but the recipe states 1/2 cup. Which is it? Wish you’d proofread better. This kind of error occurs toooooo many times.
Hi there,
It’s just 1 stick of butter in the recipe. Please let me know if you have any other questions, I hope you love these bars!