Melt the chocolate chips in a double boiler or microwave, stirring frequently until smooth.
Spoon melted chocolate into silicone molds, coating each half evenly. Chill in the freezer for 10 minutes.
Carefully remove chocolate halves from the molds. Fill one half with hot chocolate mix, marshmallows, and sprinkles (if using).
Heat the edges of the other half on a warm plate or pan to slightly melt the edges. Gently press onto the filled half to seal. Smooth any seams with a warm finger or spatula.
Refrigerate for 5 minutes to set. To use, place a bomb in a mug and pour 6 oz of hot milk over it. Stir and enjoy!
Notes
These can be stored in an airtight container at room temperature for up to a week.