Place 8-10 chocolate candy melts into the half spheres of the mold. Microwave for 30-60 seconds, until the chocolates are glossy and melted together. Stir the chocolate in the molds and use the back of the spoon to 'brush' the chocolate up to the edges of the mold.
Flip the mold over onto a sheet of parchment or silicone mat. Let the excess chocolate drip out of the molds - this will create a thin shell of chocolate. Flip the molds upright and immediately place into the fridge to set, about 10-15 minutes. Reserve the chocolate drippings - these can be remelted and used for more bombs.
Microwave a plate by itself for 30-60 seconds until it is warm but not burning hot. Arrange a few cupcake liners near the plate for ease of transferring.
While wearing latex gloves (to avoid leaving fingerprints), remove one half of the sphere from the mold. Place it seam side down on the plate for about 3-5 seconds to get the edge melted. DO NOT LEAVE THE CHOCOLATE ON THE PLATE FOR LONGER OR IT WILL MELT TOO MUCH TO FORM A SPHERE.
Place the first half of the sphere in a cupcake liner with the melted edge facing up. Add about 1/2 - 1 teaspoon of hot chocolate mix into the sphere. Then place 1-2 tablespoons of mini marshmallows and 1-2 tablespoons of mini dehydrated marshmallows into the cavity.
Remove the other half of the sphere and place it on the still warm plate for 3-5 seconds to melt the edge. Quickly place it directly on top of the other filled half and press very gently so that the melted edges stick together. Make sure there are no open edges. It's okay if the seam feels weak - it will be strengthened with the decorative topping. Chill and repeat the first steps until you have about a dozen chocolate bombs - or however many you need.
When all of the chocolate bombs have been assembled, melt the colored candy melts in plastic piping baggies. Cool for a minute or two so that the baggies are melted but cool enough to be handled. DO NOT USE PIPING HOT CANDY MELTS OR THEY WILL MELT THROUGH THE CHOCOLATE.
Snip the ends of the baggies and drizzle the green, red and white candies over the cocoa bombs. While still wet, sprinkle on the mini dehydrated marshmallows, sprinkles or other festive toppings as desired. Enjoy!