Place the chocolate in a heatproof bowl and set over a saucepan of gently simmering water. Stir occasionally until melted. Remove from the heat. Tip the hundreds and thousands into a shallow dish. Thread the marshmallows onto the ends of the wooden skewers. Dip half of them in the melted chocolate, then in the hundreds and thousands. Leave to cool and set on sheets of nonstick baking paper before serving on plates.