Chocolate Marshmallow Radio Bars

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These Chocolate Marshmallow Radio Bars feature a chocolate cake base topped with a scoop of marshmallow buttercream…oh yeah, and then they’re covered in a chocolate glaze!

To the best of my knowledge, radio bars are a uniquely upstate New York thing.  More specifically, they’re a uniquely capital region of upstate New York thing.  More specifically, they’re a unique creation of one of the bakeries here in town.  Googling ‘radio bars’ only comes back with a sparse handful of results.  When was the last time you googled anything and came back with only a few hits?  I thought Google was broken.  Nope, it just turns out that radio bars aren’t as widespread as I thought.

So what is a radio bar?  Radio bars are pieces of chocolate cake topped with a spoonful (a ‘blop’ if you would) of frosting and then covered in a chocolate glaze.  I have no idea why they’re called radio bars.  I was thinking maybe they look like those old-timey radios?  But they really don’t.  So who knows how they got the name…and who cares!  All I know is they are delicious.  I can assure you with 100% certainty that these Chocolate Marshmallow Radio Bars will be a new favorite!

I was first introduced to radio bars when I was working at a local bakery right after we moved up here.  I’d taken a couple of professional baking classes at the local culinary school, and I decided it might be fun to open a bakery of my own.  I got a job working at a small ‘mom-and-pop’ bakery, and I’m glad I did…I quickly realized that I didn’t want to run my own bakery.  The quality of this particular bakery was downright bad.  Gordon Ramsay would’ve had a field day with this place!  But the one good thing that came out of those few months of being a semi-professional baker?  Radio bars.  (For the record, this bakery is not the original creator of the radio bar.  And this bakery is now thankfully out of business.)

“I hate you.”  Those were the words uttered by Angie after just one bite of these Chocolate Marshmallow Radio Bars.  We’re always careful with what we eat around here, and I had packed up these radio bars to send to her breakroom at work the next day.  But there was that one radio bar with a bite out of it, and I saved that one back for us.  Laura was right (as always often.)  I hated myself for wrapping up all of those radio bars.  Then again, I’m pretty sure her coworkers were quite pleased to walk into the break room and find a tray of these Chocolate Marshmallow Radio Bars!

Full disclosure: these bars are a bit of a process to make.  They’re not difficult by any means.  They just require a number of steps.  And after each step, it’s important to refrigerate (or ideally freeze) the bars so that the pourable frosting doesn’t turn the bars into an ooey, gooey mess.  Although, let’s be honest, I’d be ok with an ooey, gooey mess of radio bars.  Just hand me a fork, and I’ll clean up that problem!  But if you actually want to serve these bars to family or friends, then I do highly recommend taking the time to refrigerate/freeze the bars in between each step.  The result is worth it.  Trust me!

I hope you enjoy these Chocolate Marshmallow Radio Bars as much as we did!  They’re delicious, and I’m definitely filing this recipe away for when I need to take a fun dessert somewhere.  If you make this dessert, make sure to swing back by and leave a comment!   Happy baking, my friends!

These Chocolate Marshmallow Radio Bars feature a chocolate cake base topped with a scoop of marshmallow buttercream…oh yeah, and then they’re covered in a chocolate glaze!

Prep Time:15 minutes

Cook Time:40 minutes

Total Time: 55 minutes

Servings:  12 squares

Calories: 931kcal


For the Chocolate Cake

  • 2 cups all-purpose flour
  • 1½ tsp baking soda
  • 1 tsp salt
  • ⅔ cup cocoa powder
  • ⅔ cup hot coffee or hot water
  • ⅔ cup milk
  • 2 tsp vanilla extract
  • ¾ cup unsalted butter room temperature
  • 1 cup granulated sugar
  • 1 cup brown sugar
  • 3 large eggs

For the Marshmallow Buttercream

  • ¾ cup unsalted butter room temperature
  • 1¼ cups marshmallow fluff
  • 1 tsp vanilla extract
  • 1 tsp milk
  • 2½ cups powdered sugar

For the Chocolate Frosting

  • 2½ cups powdered sugar
  • ½ cup milk
  • 1 tsp vanilla extract
  • 1 cup granulated sugar
  • ⅓ cup cocoa powder
  • ⅓ cup corn syrup
  • ¼ tsp salt
  • 1 cup unsalted butter


For the Chocolate Cake

  1. Preheat oven to 350°F.
  2. Grease and flour sides of a 9”x13”baking pan; line bottom of pan with parchment paper. Set pan aside.
  3. Using a medium mixing bowl, sift together the flour, baking soda and salt; set aside.
  4. In a separate bowl, whisk together the cocoa powder and coffee until well combined. Stir in the milk and vanilla extract; set aside.
  5. Using a countertop mixer fitted with the paddle attachment, cream the butter and both sugars together on medium-high speed until light and fluffy (~4-5 minutes).
  6. Add the eggs one at a time, mixing until just incorporated after each addition.
  7. Add half of the flour mixture to the bowl; mix on low speed until just combined.
  8. Add half of the liquid mixture; mix on low speed until just combined.
  9. Repeat with the remaining flour and liquid.
  10. Pour batter into prepared pan. Bake at 350°F for 36-38 minutes, or until a toothpick inserted into the center of the cake comes out mostly clean.
  11. Let cake cool in the pan for at least 30 minutes, then cover and transfer to a freezer for at least 60 minutes, or overnight.

For the Marshmallow Buttercream

  1. Using a countertop mixer, cream together the butter and marshmallow fluff until smooth (~2-3 minutes on medium high speed).
  2. Add vanilla and milk and powdered sugar 1 cup at a time, mixing well after each addition.
  3. Place buttercream in refrigerator for 15-20 minutes.

For the Chocolate Frosting

  1. Using a medium heatproof mixing bowl, whisk together powdered sugar, milk and vanilla extract; set bowl aside.
  2. Using a medium saucepan, add sugar, cocoa powder, corn syrup, salt and ½ cup (1 stick) of butter. Place over medium-high heat and bring to a boil, stirring occasionally. Continue cooking until mixture reaches 240°F.
  3. Remove saucepan from heat and slowly pour liquid into bowl with the powdered sugar, whisking constantly as you pour. Add remaining ½ cup (1 stick) of butter and stir until butter has completely melted.
  4. Let mixture cool until just warm to the touch.

To Assemble

  1. Remove the chocolate cake from the freezer and slice into 3”x3” squares.
  2. Using two spoons (or a large piping tip), place a large scoop of buttercream onto the center of each square. Place squares back in freezer for 30 minutes.
  3. Remove squares from freezer and pour warm (not hot) frosting evenly on top. (Tip: Place squares on a cooling rack set over a baking pan. That way, the pan catches any excess frosting as it’s poured.)
  4. Place squares back in freezer for 15 minutes, or until chocolate frosting has hardened.
  5. Serve chilled and store any leftovers in the refrigerator.

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