Method
Preparation of Cake
Preheat the oven to 350°F (175°C). Grease and flour a round cake pan.
In a bowl, combine flour, sugar, cocoa powder, baking powder, and salt.
In another bowl, beat together softened butter, eggs, and milk until smooth.
Gradually blend the dry ingredients into the wet mixture until just combined.
Pour the batter into the prepared cake pan.
Bake for 30-35 minutes or until a toothpick inserted comes out clean.
Let the cake cool completely.
Preparation of Mousse
Meanwhile, melt chocolate chips in a microwave-safe bowl and let cool slightly.
Whip the heavy cream with vanilla until soft peaks form.
Fold the melted chocolate into the whipped cream until there are no streaks.
Spread the chocolate mousse on top of the cooled cake.
Chill for at least 2 hours before serving.
Notes
Store any leftover cake in the refrigerator covered with plastic wrap or in an airtight container. Best consumed within 3-4 days.