Make the hot chocolate powder by combining all of the ingredients (sugar, cocoa powder, chopped white chocolate, and powdered milk) in a small bowl. Stir to combine. Set aside until ready to use.

Melt the white chocolate bark according to the package directions.

Add 1-2 tablespoons of melted white chocolate to each well and spread it out evenly using a spoon or offset spatula. Make sure to have a thick layer around the top edges so the chocolate bombs aren’t too brittle.

Place the wells in the fridge until the chocolate has completely hardened-- about five minutes. Carefully remove the chocolates from the mold.

Fill half of the molds with 1-2 tablespoons of cocoa mix and a few mini marshmallows.

Heat a nonstick pan over medium-high heat for 1-2 minutes. Then, remove it from the pan. If the pan ever becomes too cool, just reheat it for another minute.

Place an empty well of chocolate rim side down on the hot pan for 1-2 seconds, or you see the edges start to melt. Remove it from the pan and place it on top of a filled well to seal the two together.

Decorate with a chocolate drizzle and/or sprinkles. Store in the refrigerator until ready to use.

To serve, add one hot chocolate bomb to a mug. Fill the mug with 8 ounces (1 cup) hot milk and stir. Garnish with additional marshmallows, if desired.