Place the White Chocolate in a Microwave safe bowl, and melt until smooth and creamy. Stir well.
Divide the melted Chocolate into 5 small cups, and place a drop of Food Coloring Gel in cups, making 5 pastel colors, one color in each cup.
Stir the chocolate until the colors are smooth, and add a little more food coloring gel if you want the colors brighter. (If you only want to use 2 or 3 colors, only use 2 or 3 cups to divide the chocolate)
Spoon or ladle into the molds, making sure to coat the inside of the molds.
Pour excess chocolate back into the bowl, and place the molds in the refrigerator, and let harden for 15 minutes. Remove molds from the refrigerator, and carefully remove chocolate from molds, placing 6 half balls in a row on a cookie sheet. These will be the bottom parts or half of the Cocoa bombs.
Heat a nonstick skillet, on low, and place one-half ball with the open side down, melting just the edges for a few seconds, remove, place on a cookie sheet, and fill the Ball with the powdered Cocoa, a Conversation Heart, and Mini Marshmallows.
Repeat, until all 6 Balls are done.
Place the other half of the chocolate balls in the skillet, with the open side down, and melt just the edges of the ball. Remove from the Skillet, and immediately place on one of the chocolate balls, filled with the cocoa, etc., making the top of the ball/bomb.
Hold in place for a few seconds to make sure the top and bottom are melted together.
When all the Cocoa Bombs have been filled and melted together, place them in the refrigerator for 30 minutes, until chocolate is completely set.
Remove from the Refrigerator, and set the cookie sheet on the counter.
Place more White Chocolate in a microwave-safe bowl, and microwave at 15-second intervals until the chocolate melts. Place the melted chocolate in a Pastry bag, and pipe the White Chocolate over the Cocoa Bombs (see photo) and place a Conversation Heart on the top.
Place one Hot Cocoa Bomb in the bottom of a large mug, and pour heated milk over the top.
Cocoa Bomb will melt and bubble, and marshmallows will float to the top.
Stir the powdered cocoa, and Enjoy!