Remove the molds from the fridge, gently turn them over, and carefully remove each chocolate shell. Place them on a metal tray. Remember to take care not to crack the shells as you remove them.
Fill six chocolate shells with 2tsp (10g) of hot chocolate powder and a couple mini marshmallow ensuring not to over-fill.
Microwave an oven-safe plate for a minute, remove with oven mit and place on the counter.
Place one unfilled shell face down on the plate for a few seconds to melt the edge, then place on top of a filled shell. Hold together for 10 seconds to join them. Seal any gaps with a hot spoon dipped in left over melted chocolate.