01 - Place chopped chocolate in a microwave-safe bowl. Microwave in 20-second intervals, stirring between each, until the chocolate is completely melted and smooth.
02 - Using a pastry brush or spoon, coat the inside of each half-sphere silicone mold (about 2.5 inches in diameter) with a layer of melted chocolate. Refrigerate for 5 minutes, then apply a second coat for structural strength. Chill until fully set, about 10 minutes.
03 - Gently release the chocolate shells from the molds and place them onto a cool, clean surface.
04 - Fill half of the chocolate shells with 1 tablespoon of hot cocoa mix and 6 mini marshmallows. Include chocolate chips, crushed peppermint, or sprinkles if desired.
05 - Warm a small plate in the microwave until just hot to the touch. Lightly press the edge of an empty shell half onto the plate to melt the rim, then swiftly cap a filled half with it to seal. Smooth the seam with a gloved finger, if necessary.
06 - Drizzle sealed bombs with melted white chocolate. Add sprinkles or edible glitter according to preference and let set at room temperature.
07 - To serve, place a hot chocolate bomb in a mug and pour 1 cup of steaming hot milk over it. Stir until the bomb dissolves and the drink becomes creamy.