Place chocolate in a microwave-safe bowl and melt in 30-second intervals, or use a double boiler to melt chocolate.
Place 1 Tbsp of melted chocolate into each half-bomb mold and spread with a finger or, using the bottom of your tablespoon measuring spoon, press the chocolate up the sides of the mold, keeping it thick but even. Repeat with all silicone mold halves. Reserve the remaining melted chocolate. Fill the half molds with the miniature marshmallows and drizzle a little chocolate on top of them so they will stay in place when turned over.
Place the chocolate-filled molds into the freezer for 5 minutes or until set and can be removed. Remove molds from the freezer, gently peel the silicone away from the marshmallow chocolate cups, and set aside.
Place 2 or 3 hot chocolate bombs into a mug, pour the hot milk of choice over the chocolate bombs, and stir to combine. Enjoy your Hot Chocolate Bombs!