Introduction

These Chocolate Mousse Brownies combine a rich, fudgy brownie base with a light and fluffy chocolate mousse topping. Perfect for chocolate lovers looking for an indulgent dessert that balances dense and airy textures.

Three square pieces of chocolate brownies are stacked on a white plate, each with two distinct layers: a thick, dark, dense brownie base with a moist and slightly crumbly texture, topped with a lighter, fluffy layer of chocolate frosting that has a smooth, creamy surface with soft swirls. The background shows a soft white marbled texture and a blurred white ceramic cup, adding a clean and bright feel to the image. Photo taken with an iphone --ar 4:5 --v 7

Ingredients

4 ounces semisweet chocolate baking bar, chopped
¼ cup salted butter
⅓ cup vegetable oil
1 ½ cups granulated sugar
2 eggs, room temperature
2 teaspoons pure vanilla extract
¾ cup all purpose flour, spooned and leveled
½ cup unsweetened Dutch processed cocoa powder
½ teaspoon baking powder
½ teaspoon table salt
4 ounces semisweet chocolate baking bar, chopped
1 cup mini marshmallows
¼ cup whole milk
1 tablespoon whole milk
1 ¼ cup cold heavy cream
Chocolate syrup for drizzling (optional garnish)

Instructions

Step 1: Preheat your oven to 350°F (175°C). Line a 9×9 inch baking pan with parchment paper, leaving an overhang on the sides for easy removal.
Step 2: In a medium microwave-safe bowl, melt 4 ounces chopped semisweet chocolate and ¼ cup salted butter. Heat in 20 second intervals or use a double boiler, stirring until smooth. Stir in ⅓ cup vegetable oil.
Step 3: In a large mixing bowl, add 1 ½ cups sugar. Whisk in the chocolate mixture until fully combined—the batter will be thick.
Step 4: Whisk in 2 eggs one at a time just until incorporated; avoid overbeating to prevent excess air.
Step 5: Add 2 teaspoons vanilla extract and mix gently.
Step 6: Sift together ¾ cup all purpose flour, ½ cup cocoa powder, ½ teaspoon baking powder, and ½ teaspoon salt. Fold the dry ingredients into the wet mixture until no streaks remain.
Step 7: Spread the batter evenly in the prepared pan. Bake for 22 to 25 minutes, until edges are set but the center still looks slightly underbaked.
Step 8: Let the brownies cool completely in the pan while you prepare the mousse.
Step 9: Place a mixing bowl and whisk attachment or beaters in the freezer for about 10 minutes to chill.
Step 10: In a medium saucepan over low heat, combine 4 ounces chopped semisweet chocolate, 1 cup mini marshmallows, and ¼ cup whole milk. Stir constantly until melted and smooth.
Step 11: Allow the chocolate mixture to cool to room temperature to prevent deflating the whipped cream.
Step 12: In a large bowl, beat 1 ¼ cup cold heavy cream with an electric mixer until soft peaks form.
Step 13: Lower mixer speed to low and add the cooled chocolate mixture. Increase speed to high and beat until stiff peaks form. Be careful not to overwhip.
Step 14: Spread the mousse evenly over the cooled brownies using a spatula. Cover and refrigerate for at least 2 hours to set.
Step 15: Remove from fridge, use the parchment overhang to lift brownies out of the pan, and slice into 12 squares. Drizzle with chocolate syrup if desired before serving.

Tips & Variations

For a nutty twist, fold ½ cup chopped toasted walnuts or pecans into the brownie batter before baking.
Use a high-quality Dutch-processed cocoa powder for a richer chocolate flavor.
Be sure the chocolate mixture is fully cooled before mixing with whipped cream to maintain mousse volume.
Mini marshmallows can be replaced with marshmallow fluff melted gently into the chocolate for convenience.
For an intense chocolate vibe, add a pinch of espresso powder to the batter.

Storage

Store the brownies covered in the refrigerator for up to 3 days to keep the mousse fresh. Bring to room temperature for 15 minutes before serving if preferred. Leftovers can also be frozen tightly wrapped for up to 1 month; thaw in the fridge overnight.

How to Serve

Three square pieces of chocolate brownies are stacked on a white plate, each piece showing two layers: a dense, dark brown brownie base with a slightly crumbly texture, and a thick, creamy light brown chocolate frosting on top with soft swirled patterns. The stack is centered on a white marbled surface with a blurred white cup in the background. Photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I make the brownies ahead of time?

Yes, you can bake the brownies a day ahead and prepare the mousse topping the next day before serving to keep the mousse light and fresh.

What if I don’t have a stand mixer?

A handheld mixer works perfectly fine for whipping the cream and combining the mousse ingredients. Just make sure your mixing bowl is well chilled.