Turn your instant pot onto sauté mode. Place one and a half cups of water inside your instant pot. Place a glass bowl that will fit in your instant pot as it will act as a double broiler. (NOTE: you can also melt the candy in the microwave - just follow the instructions on the bag!)
Add in your candy melts to the bowl. Continue to mix until the chocolate has completely melted.
Lightly grease the inside of your silicone molds. Add chocolate to your molds making sure that chocolate is completely coating the mold on the inside (you want the chocolate layer kind of thick). Place in the freezer for about five minutes.
Remove your molds from the freezer. Add a half a tablespoon of cocoa powder and about 4 marshmallows per mold.
Add more of your melted chocolate on top of the marshmallows to close the mold and lock the cocoa and marshmallows from coming out. Return to the freezer for about 5 to 10 minutes.
Remove your cocoa bombs by pushing on the silicone side of the mold until the bomb pops out.
With a spoon, drizzle your remaining chocolate over the bombs. Immediately add your sprinkles before the chocolate hardens.
Please one or two bombs in your favorite mug and pour hot milk over it to melt the chocolate releasing the hot cocoa and marshmallows.