If you are using a chocolate bar, chop the chocolate into small pieces.
Place the chocolate in a microwave-safe bowl and heat for 30 seconds. Remove the chocolate from the microwave and stir the chocolate.
Heat the chocolate again in 15-second intervals, making sure to stir the chocolate each time until it is fully melted. Use an instant thermometer to check the temperature, it should read 90°F.
Use a damp paper towel to make sure the silicone molds are clean.
Pour a spoonful of the melted chocolate into the mold and spread the chocolate inside of the mold. Be sure there are no empty spaces and the mold is evenly coated.
Once all the mold openings are filled, place the mold carefully into the freezer. Let the chocolate set for 5 minutes.
Remove the mold from the freezer. Add a small amount of chocolate along the top perimeter of the chocolate mold to make it thicker. Place the mold back into the freezer for 5-10 minutes.
Remove the chocolate from the molds carefully and place it on a parchment-lined plate. The easiest way to make the bombs is to flip the silicone mat over and use the spaces to hold the mold. Then, fill the mold with 1 tbsp hot chocolate and marshmallows.
Seal the spheres together by piping melted chocolate around the edge of one sphere and gently pressing it onto the filled chocolate sphere. Or, you can slightly melt one sphere using a warm plate (warm an empty plate in the microwave for 30 seconds), and gently press the spheres together.
You can use your gloved fingers to gently smooth out any chocolate along the center of the ball.
Place the Chocolate Bombs in the fridge for 3-5 minutes to completely set.
Decorate with melted white chocolate, sprinkles, crushed peppermint, or any of your favorite toppings.
Enjoy!