1. Prepare two heatproof glasses ﬁrst. Place the chopped chocolate in a heatproof bowl set over a pan of simmering water and heat over a low heat until melted — do not let the base of the bowl touch the surface of the water. Carefully dip the rims of each glass into the chocolate.
2. Place the cracker/biscuit crumbs on a plate and dip the chocolate-coated rim of each glass in the crumbs to coat. Set aside until you are ready to serve.
3. Spoon the remaining melted chocolate into a saucepan with the milk and cream, and heat over low heat, whisking all the time. Pour the hot chocolate into the prepared glasses, taking care not to pour over the chocolate-crumb rim decoration.
4. Place each marshmallow on a fork and toast with the blow torch to caramelize. Take care not to burn the marshmallows. While the marshmallows are still warm, place one on top of each drink. Serve at once.