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Chocolate Mousse Brownies Recipe – Fudgy, Creamy, and Decadent

Learn how to make layered Chocolate Mousse Brownies with fudgy base, creamy mousse, and glossy ganache. Perfect make-ahead dessert for chocolate lovers.
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Prep Time 30 minutes
Chill Time 3 hours
Total Time 3 hours 30 minutes
Course Dessert
Cuisine American
Servings 12
Calories 350 kcal

Ingredients
  

For the Brownie Base

  • ½ cup (115g) unsalted butter, melted
  • 1 cup (200g) granulated sugar
  • 2 large eggs
  • 1 tsp vanilla extract
  • ⅓ cup (40g) unsweetened cocoa powder
  • ½ cup (65g) all-purpose flour
  • ¼ tsp salt
  • ¼ tsp baking powder

For the Chocolate Mousse

  • 1½ cups (350ml) heavy whipping cream, chilled
  • 8 oz (225g) semisweet chocolate, finely chopped
  • 3-4 tbsp (45–60ml) milk (start with 3, add 1 more if chocolate resists melting)
  • 2 tbsp (25g) powdered sugar

For the Ganache Topping

  • 4 oz (115g) semisweet chocolate, finely chopped
  • ½ cup pped½ cup

Instructions
 

Bake the Brownie Base

  • Preheat oven to 350°F (175°C). Line an 8×8-inch (20×20 cm) pan with parchment paper, leaving a small overhang for easy lifting.
  • In a bowl, whisk together melted butter, sugar, eggs, and vanilla until smooth.
  • Sift in cocoa, flour, salt, and baking powder. Gently fold — no overmixing; the goal is silky, not stiff.
  • Pour batter into pan and spread evenly.
  • Bake for 20–25 minutes, or until a toothpick comes out with a few moist crumbs.
  • Let the brownie cool completely in the pan before moving to the next layer.

Prepare the Chocolate Mousse

  • Heat milk until steaming (not boiling). Pour over chopped chocolate in a heatproof bowl.
  • Let it sit for 2 minutes, then stir until glossy and smooth. If lumps remain, add another tablespoon of warm milk.
  • Allow to cool to room temperature — it should be fluid but not hot.
  • In another bowl, whip chilled heavy cream with powdered sugar until soft peaks form.
  • Fold a spoonful of whipped cream into the chocolate mixture first to balance temperature, then gently fold in the rest until no streaks remain.
  • Spread mousse evenly over the cooled brownie base.
  • Refrigerate for at least 2 hours to set.

Finish With the Ganache

  • Place chopped chocolate in a bowl.
  • Heat heavy cream until just simmering, then pour over chocolate.
  • Wait 2–3 minutes, then stir until smooth and shiny.
  • Pour ganache over the chilled mousse and smooth it with an offset spatula.
  • Return to fridge for 1 hour, or until firm enough to slice cleanly.