Chocolate Sauce: Melt chocolate in a bowl over simmering water, until completely smooth. Heat butter, double cream and sugar in a saucepan until combined. Remove from heat then stir in the melted chocolate.
Sundae: Get out four sundae glasses. Add the ingredients in to each glass in the following order: scoop of ice cream, Maltesers, another scoop of ice cream, marshmallows, another scoop of ice cream and then the berries.
Pour some of the hot chocolate sauce over each sundae.