In two separate, medium sized, microwave safe bowls, melt the red and white candy melts in 30 second increments, stirring in between.
Once melted, drizzle some white candy melt into the bottom of your silicone mold. Next, spoon some red candy melt into each mold, enough to fill the mold ½ full and spread it around the mold as evenly as possible. Be sure there is enough candy melt in each mold to thickly cover all sides so there are no thin spots.
Using an offset spatula, remove the extra candy melt from the top of the mold, smoothing the edges of the hearts in the process.
Let set until hardened, about 10 minutes. If the top edge of the heart feels thin or delicate, spread just a little more of the red candy melt to reinforce it and let set until hardened. Gently remove the hearts from the mold.
In 8 of the heart halves, place 2 Tbsp of hot chocolate powder, several mini marshmallows and some sprinkles for extra fun.
Warm a small plate in the microwave. Remove from microwave and place the opposing half of the heart on the plate for 3-5 seconds to let the edges melt.
Match the empty half with the filled half and gently press them together. Run a clean finger along the seam to smooth it out. If the halves don’t stay together, you can warm a metal knife by running it under hot water then run the warm knife over the edge of the filled half while the empty half is on the plate.
Once all of the hot cocoa bombs are together, serve and enjoy or package and give away!