Put the white candy melts into a microwave-safe bowl. Once added, melt them according to the directions on the package.
Put 2 tablespoons of the melted candy into half of the bath bomb mold. Use the back of your spoon to press the melted chocolate up and around the sides of the mold. You're going to want to make it even and thick. Do this for all 12 halves.
Pop the bomb molds into your freezer for 5 minutes.
Once the time has passed, remove the molds from the freezer and give the sides a little tap. This should loosen up the chocolate and bit to where you can push on one side of the frozen chocolate. This should help it slide out easier.
Take 6 of the chocolate molds and add in 2 tablespoons of the hot chocolate mix, 1 teaspoon of sprinkles, and 6-8 mini marshmallows.
Grab a plate or a bowl with a flat bottom and place it in the microwave long enough for the surface to be warm to the touch.
Using one of the empty bomb molds, take and place it open side down on the plate. Hold it there for about 10 seconds. This should melt the very edge of the mold slowly.
Once melted, take it and press it down onto the very top of the filled mold half. They should stick together, creating a full circle.
Grab the gel and drizzle the icing over the top of the cocoa bombs. Follow that up with sprinkles.
After that is done and they are decorated, put them in the freezer for 5 minutes to firm.