Put the biscuits in a freezer bag and seal it. Crumble the biscuits with a dough roll and place them on a saucer. Pour chocolate syrup onto a second saucer. Dip glasses with the rim in syrup first, let them drip off a little and then turn them in the biscuit crumbs. Place glasses (à approx. 250 ml) in the freezer for about 30 minutes.
Mix vodka, cocoa and cream and chill. Put 1 marshmallow on each wooden skewer and scorch briefly with a kitchen gas burner. Take glasses out of the freezer, pour in martini and serve immediately with 1 marshmallow each.