Finely chop chocolate and place in a microwave-safe bowl. Heat in the microwave for 25 seconds.

Remove from the microwave and stir thoroughly, scraping the sides and bottom of the bowl with a rubber spatula. It will seem like basically nothing has happened, stir anyway.

Return chocolate to the microwave and heat for 15 seconds, remove and stir thoroughly again. Repeat until chocolate begins to melt. Once it starts to melt, start using your thermometer to watch the temperature of the chocolate. It is important that you heat the chocolate above 87F (30C) but keep the temperature below 91F (33C) to temper the chocolate so that it’s easy to work with and yields shells that are smooth and shiny. If you’re at or close to 90F (32C) and the chocolate still has some small clumps of unmelted chocolate in it, just keep mixing and it should melt. If it’s still not melting, heat in 5-second spurts.

Once your chocolate is in the right temperature range, use a spoon or paintbrush to thoroughly coat the entire inside of each sphere mold (make sure to get the edges!). If chocolate starts to become firm, return it to the microwave, heating in 5-second spurts and stirring. Remember to keep it in that sweet spot!

Transfer to the refrigerator and chill for 5 minutes. Remove from the fridge and touch up any places where the chocolate is thin (especially the edges!) or any holes that may be in your coating.

Return to fridge again for another 5 minutes. Meanwhile, heat a small pan on the stovetop over low heat.

Remove chocolate from refrigerator and carefully remove from molds. Briefly touch the rim of one half-sphere on the surface of the pan until it just starts to melt (this will take only a second and gives you a smooth surface so your "bomb" will have a smooth seam).

Fill with two teaspoons of cocoa mix and mini marshmallows/other fillings, if desired.

Take another half-sphere and briefly touch the edge against the surface of the pan and immediately, carefully, but firmly press onto the edge of the filled half to form a full sphere. Hold for a second to give the chocolate a minute to harden

If desired, drizzle with additional chocolate (I used white chocolate) and sprinkles or other decorations.

To serve, place in a mug and then slowly pour steaming hot milk over the hot chocolate bomb (or just drop the cocoa bomb in a mug of steaming milk). I've found that 8-10 oz of milk seems to be just the right amount.

Enjoy! These make great gifts!