Finely chop your chocolate using a sharp knife and place in a large heatproof bowl.

Heat for 30 seconds at a medium-high heat (I use power level 7 out of 10).

Remove from the microwave and stir the chocolate. It won't have melted much yet, but heating it slowly and stirring between helps evenly heat the chocolate and makes sure certain areas don't overheat/overcook.

Heat for an additional 15 seconds on medium-high power and stir again. If possible, check the temperature of the chocolate with a food thermometer after you heat it to make sure it doesn't go above 90 F / 32 C.

Repeat until the chocolate is mostly but not fully melted. The heat from the bowl will melt the remaining bits as the chocolate sits.

Let the chocolate sit for a couple minutes then give it one more more stir, making sure it's nice and smooth. Use a clean / food-safe paint brush to brush an even layer of chocolate in each indention in the silicone mold.

Chill the mold in the fridge for about 3 minutes or until the chocolate is firm to the touch.

Paint on a second layer of melted chocolate, being sure to add a little extra around the rim of each sphere. This will make them easier to remove from the silicone mold and help prevent them from breaking.

Refrigerate for 3-5 minutes until the chocolate has set, then carefully remove the chocolate from the silicone mold.

Fill half of the spheres with 1 tsp of hot chocolate and a 1 tsp of mini marshmallows.

Place the remaining tempered chocolate in a small piping bag and pipe a ring around each filled semi-sphere.

Top with a second sphere and press together to create a seal. If your seal doesn't look fully closed at this point, pipe a ring of chocolate over it to make sure it's fully closed.

Roll each hot chocolate bomb in a bowl of sprinkles to cover the seal, then drop into a hot cup of milk and enjoy!