1. Start by melting the 8 ounces of chocolate gently in a double boiler or microwave. If using a microwave, heat in 30-second bursts, stirring in between to avoid overheating and seizing. The chocolate should be smooth and glossy.
2. Using a silicone half-sphere mold (about 2 inches in diameter), spoon about a tablespoon of melted chocolate into each cavity. Tilt the mold to coat the sides evenly, making sure to build a thick enough shell to hold the fillings without breaking. Chill in the fridge for about 10 minutes to set.
3. Once the first layer is firm, add a second thin layer of chocolate for extra strength. Chill again for 10 minutes.
4. Carefully remove the chocolate halves from the mold. Here’s a tip I learned the hard way: if they don’t release easily, give them a little extra time to chill or gently warm the mold with your hands to loosen.
5. Fill half of the spheres with 1 teaspoon of hot cocoa mix and a small handful of mini marshmallows. You can sprinkle a pinch of cinnamon or a few drops of vanilla extract inside for added flavor.
6. Warm the extra chocolate (2 ounces) slightly to use as “glue.” Take an empty half-sphere and dip the rim briefly into the melted chocolate, then quickly press it onto a filled half to seal. Hold gently until set.
7. Place the sealed cocoa bombs back in the fridge for 15 minutes to harden completely.
8. To enjoy, heat a mug of milk (about 8 ounces) until steaming but not boiling. Drop in one cocoa bomb and watch it melt, stirring gently to combine the melted chocolate, cocoa mix, and marshmallows into a creamy, dreamy cup of hot chocolate.

From experience, I recommend having a towel handy—the melting chocolate can get a little messy, but that’s part of the fun!