Melt chocolate and spread it into the silicone molds, coating each cavity entirely with at least two layers of chocolate.
Refrigerate molds until chocolate is solid (at least 5 minutes), then carefull remove the chocolate from the mold.
Fill one half of molded chocolate with 2 tablespoons of cocoa mix and a handful of mini marshmallows.
Then, gently press the edge of an empty half onto a hot plate or pan to just melt the chocolate.
Join the two halves together to seal the bomb.
Repeat steps 3-5 to make the rest.
Decorate the outsides with drizzles of colored melting chocolate, crushed candy, etc.
When ready to serve, place one bomb into a mug of steaming hot milk and watch the magic happen.