Melt the chocolate in a heatproof bowl. Carefully add to the mould and leave to set in the fridge.
Once set assemble the pumpkin by using melted chocolate to "glue" the pumpkin together. Leave a space at the bottom to add the hot chocolate. Leave to set.
Then carefully add in 2 tsp of hot chocolate powder into the pumpkin. Then seal the bottom of the pumpkin with melted chocolate.
Leave to set. Once set drop into a cup of warm milk and top with marshmallows. Ta-da!