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Fudgy hot chocolate brownies topped with marshmallows and cocoa frosting on a nice plate.

Hot Chocolate Brownies

These Hot Chocolate Brownies are ultra-fudgy, loaded with melty mini marshmallows, and finished with a silky hot-chocolate-style cocoa frosting. They taste like a cozy mug of hot cocoa in brownie form — gooey, rich, and perfect for winter baking, gifting, or holiday parties.
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Prep Time 15 minutes
Cook Time 35 minutes
cooling time 15 minutes
Total Time 1 hour 5 minutes
Servings: 12
Course: Dessert
Cuisine: American
Calories: 225

Ingredients
  

For the Brownies
  • ½ cup unsalted butter 1 stick
  • ¾ cup semi-sweet chocolate chips
  • 1 cup granulated sugar
  • ½ cup brown sugar
  • 2 large eggs
  • 1 egg yolk
  • 1 ½ teaspoons vanilla extract
  • ½ cup unsweetened cocoa powder
  • ¾ cup all-purpose flour
  • ½ teaspoon baking powder
  • ½ teaspoon salt
  • 1 ¾ cup mini marshmallows (1 cup for batter- ¾ cup topping)
For the Hot Chocolate Frosting
  • 1 ½ cups powdered sugar
  • ¼ cup unsweetened cocoa powder
  • 4 tablespoons unsalted butter melted
  • ¼ cup hot milk or hot water
  • ½ teaspoon vanilla extract
  • Pinch of salt

Equipment

  • Mixing Bowl
  • Whisk

Method
 

Preheat
  1. Preheat oven to 350°F.
  2. Line an 8×8 pan with parchment paper and lightly spray.
Melt Butter + Chocolate
  1. In a heat-safe bowl, melt the butter and chocolate chips together (microwave or stovetop).
  2. Stir until smooth and glossy.
  3. Let cool 2–3 minutes.
Mix Wet Ingredients
  1. Whisk in: granulated sugar, brown sugar, eggs, egg yolk and vanilla.
  2. The mixture should look thick and shiny.
  3. Mix in melted and cooled chocolate & butter .
Add Dry Ingredients
  1. Whisk in the cocoa powder.
  2. Add flour, baking powder, and salt. Stir gently until just combined.
  3. Add Marshmallows
  4. Fold in 1 cup mini marshmallows.
Bake
  1. Spread batter into the pan and smooth the top.
  2. Bake 35-40 minutes, or until the center is just set.
  3. In the last 2 minutes, sprinkle about ¾ cup of mini marshmallows on top so they puff without burning.
  4. Let brownies cool fully.
Make the Hot Chocolate Frosting
  1. Whisk powdered sugar and cocoa.
  2. Add melted butter, hot milk, vanilla, and salt.
  3. Whisk until smooth and pourable. Add more hot milk 1 teaspoon at a time if needed.
  4. Pour over cooled brownies and let set 20–30 minutes before slicing.

Notes

Don’t skip cooling before frosting:
If the brownies are even slightly warm, the frosting will melt into the top instead of creating that smooth hot-chocolate layer.
• Marshmallow tip:
Mini marshmallows melt into the batter beautifully, but the ones sprinkled on top should only bake for the final 1–2 minutes to prevent burning. They’ll stay soft and puffy.
• Fudgier vs. cakier:
For extra-fudgy brownies, pull them at the 35-minute mark when the center is just barely set. For a slightly firmer brownie, bake closer to 40 minutes.
• Pan size adjustments:
You can bake these in a 9×9 pan — just reduce baking time slightly (20–25 minutes). They’ll be a touch thinner but still perfectly fudgy.
• Peppermint version (holiday twist):
Swap the vanilla for ½ teaspoon peppermint extract and sprinkle crushed candy canes on the frosting.