Chop chocolate and melt in a double boiler or with your microwave using 30 second bursts, storring in between. You can temper the chocolate if you're making these In advance or want that shiny surface but it is not a must.
Add a spoonful of melted chocolate to your hemispherical mold and use a spoon or brush to create an even layer of chocolate all the way up to the edge. Freeze for about ten minutes.
Warm a pan over medium heat for about 30 seconds then remove from heat and carefully remove the now set chocolate from the mold . Gloves are handy of avoiding fingerprints at this stage. Carefully melt the edge on the pan and place in a cupcake paper or round cookie cutter to hold in place.
Add two tablespoons of cocoa powder to the base then top with a mound of marshmallows. Melt the bottom of another shell and place on the base. Press down gently and pipe a very thin line of melted chocolate onto the joint to seal the two halves. Smooth with your finger or a small knife.
Decorate with a drizzle or dark or white chocolate and sprinkles if desired. Repeat for the remaining chocolates.
Use a clean paintbrush to brush the chocolate evenly in the molds making sure to cover all the sides.
Let the chocolate molds set in the freezer, they set really fast (about 10 minutes).
When removing the chocolate from the mold and assembling them it's a good idea to wear gloves to avoid any fingerprints on the surface.
Instead of chocolate milk powder, you can fill these bombs with your favorite hot chocolate powder, it's also a great way to switch up the flavor by using chocolate orange hot chocolate powder, mint chocolate, salted caramel, and more! Also, see my instructions below on how to make your own hot chocolate powder at home.
Use candy melts and small piping bags to decorate your chocolate bombs. Think pink and red for Valentine's day, red, white, and green for Christmas etc.
Sprinkles, edible glitter, and chocolate chips/chunks are a great way to jazz up your cocoa bombs. Drizzle over a small amount of melted chocolate and top with sprinkles so they stick.
You can make your own hot cocoa powder by pulsing the below ingredients in your food processor or just whisking it up.