01 - Melt the chocolate in a microwave-safe bowl in 30-second intervals, stirring between each until smooth, or melt gently over simmering water using a double boiler.
02 - Use a pastry brush or spoon to evenly coat the inside of 12 silicone half-sphere molds (approximately 2 inches diameter) with a generous layer of melted chocolate.
03 - Refrigerate the coated molds for 10 minutes to set the chocolate.
04 - Add a second chocolate layer to the molds to reinforce the shells, then chill for 10 to 15 minutes until fully firm.
05 - Carefully remove the hardened chocolate half-spheres from the silicone molds.
06 - Fill 6 half-spheres with 1 tablespoon of hot cocoa mix and approximately 10 mini marshmallows each.
07 - Warm a plate in the microwave, briefly press the rim of an empty half-sphere against the warm plate to slightly melt, then immediately seal it onto a filled half-sphere. Repeat for all six bombs.
08 - Drizzle with melted chocolate or sprinkle festive toppings if desired, and allow to set.
09 - Place one cocoa bomb into a mug, pour 1 cup of hot milk over it, stir until dissolved, and enjoy.