Set up a double boiler with a heat-safe glass bowl that fits over a small pot on the stove. The glass bowl shouldn’t touch the water.
Heat about an inch of water in the pot over medium heat. Place the white chocolate wafers (all but about 8 wafers) into a heat-safe glass bowl and place it on top of the pot.
Stir the chocolate with a silicone spatula as the chocolate melts. Do not allow the chocolate to get too hot or it will scorch.
Remove from heat as soon as chocolate is half melted.
Continue stirring until all of the chocolate melts. Drop in a couple drops of green food coloring until it reaches the right color of green.
Once the chocolate has cooled to 82°F, place the bowl back on the double boiler until smooth enough to paint into the mold. Keep chocolate between 82°F and 90°F while working, if possible.
Use the back of a spoon to coat the inside of each sphere. Place the mold in the refrigerator for 5 minutes.
Remove the chocolate shells from the mold.
Place half of the molds, cup facing up, on a flat surface. Fill with 1 tablespoon hot cocoa and 1 tablespoon mini marshmallows.
Heat a small pan over low heat on the stove then turn it off. Quickly melt the rim of the unfilled mold on the pan then stick it to the filled mold to adhere them together. Working quickly, do this for all spheres.
For the drizzle on top, heat the remaining 8 chocolate wafers in a microwave safe bowl at 15 second increments in the microwave, stirring in between. When mostly melted, remove and stir until completely melted. Drop in one small drop of green food coloring to make a lighter color than the spheres. Transfer the chocolate to a small plastic baggie. Cut a very small corner off the bag. drizzle melted chocolate over the tops of your spheres and add a candy heart.