Place 2 martini glasses in the fridge and chill for 30 minutes. Place the crushed ginger biscuits onto a saucer and pour a small amount of cold water on a separate saucer. Dip the rims of the glasses into the water, then the biscuit crumbs, to decorate. Place the schnapps, Kahlua, Baileys and Amarula into a cocktail shaker, top up with ice cubes, shake well and then strain into the glasses.