Melt chocolate chips by microwaving them in a bowl for 30 seconds, stirring, then continuing to heat at 15-second intervals, and stir until the chips are all melted.
Use a spoon to dollop the melted chocolate into your molds, smoothing it around the edges until everything is covered. Set in the refrigerator for about 30 minutes, or until the chocolate is firm.
Fill your mold three-fourths full with your hot cocoa mix and optional add-ins.
Pour the remaining chocolate over top to seal the "back" of the bombs. Place mold in the fridge until the chocolate sets.
Serve in a mug, pouring hot milk over the bomb and stirring until completely melted.