Bake cake according to cake mix instructions in 2 8″ round pans. Allow to cool and set aside. This can be done several days in advance; just freeze the cakes when you’re done.

In a small bowl, combine gelatin and cold water and allow to stand for about 1 minute. While gelatin is softening, bring about 1 cup of water to a boil in the microwave and measure out 2 tablespoons. Discard the rest. Whisk the 2 tablespoons of boiling water into the softened gelatin and allow to cool slightly.

In a medium mixing bowl, combine sugar, cocoa powder, whipping cream, and vanilla. Beat with an electric mixer until medium-stiff peaks form. Mix in gelatin mixture and refrigerate for 30 minutes.

Prepare ganache (if you haven’t already) according to directions.

With a serrated knife, carefully slice the dome-iest part of each cake layer off so the layers are level. Place one layer on the serving plate and spread chocolate mousse over the cake (see note below). Sprinkle with Heath bits.

Place second layer on top of Heath bits.

Spoon ganache over the top layer, allowing it to drip down the sides.  Sprinkle with additional Heath bits and refrigerate until ready to serve. If desired, top with sweetened whipped cream before serving.