Steps
1. Preheat your oven to 350°F (175°C) and grease a square baking pan.
2. In a microwave-safe bowl, melt the butter. Add sugar, eggs, and vanilla extract. Mix until well combined.
3. In a separate bowl, whisk together the flour, cocoa powder, and salt. Gradually add the dry ingredients to the wet ingredients, stirring until just combined.
4. Pour the brownie batter into the prepared baking pan and spread evenly. Bake for 20-25 minutes or until a toothpick inserted into the center comes out with a few moist crumbs. Let it cool completely.
5. In a medium bowl, whip the heavy cream until soft peaks form. In a microwave-safe bowl, melt the chocolate chips. Pour the melted chocolate into the whipped cream, add powdered sugar and vanilla extract. Gently fold until well combined.
6. Spread the chocolate mousse over the cooled brownie layer.
7. In a small saucepan, heat the heavy cream for the ganache until it starts to simmer. Remove from heat and add the chocolate chips. Stir until smooth and glossy.
8. Pour the ganache over the chocolate mousse layer and smooth the top with a spatula.
9. Cover and refrigerate for at least 2 hours, or until set.
10. Slice into squares and serve chilled.