Melt the chocolate in a microwave safe bowl by microwaving in 15 second intervals and stirring until the chocolate is melted and pourable. Or you can temper the chocolate by melting it over water with a double boiler.
Pour a couple of tablespoons of melted chocolate into the mold and use the back of a spoon to push the melted chocolate around the molds. Go behind this with a pastry brush or food safe paint brush and brush up the mold to make sure the edges and all along the mold are completely covered.
Place the mold on a baking sheet and put in the freezer for 7-10 minutes or the refrigerator about 30 minutes. Carefully remove the chocolate from the molds by placing your fingers underneath the mold and pushing it out. Remove to a cold plate and set aside.
Heat a skillet until warm. Take one chocolate sphere and place it in the skillet for a couple of seconds until the edges melt and are even. Quickly add a tablespoon or more hot chocolate mix and a few mini marshmallows.
Take another sphere and repeat the process in the skillet. Connect the two spheres together and hold until sealed. Repeat with remaining spheres. Add garnishes, if desired.
To serve, place in a mug and pour 1 cup warmed milk over and watch all the happiness occur. Give it a stir and enjoy all the chocolatey goodness!
Store hot chocolate bombs in an airtight container in a cool place.