Place the butter in a 23 cm (9 inch) flan dish. Cover and cook on HIGH for 45 seconds, until melted. Stir in the biscuit crumbs, press into the base and sides of dish. Cook on HIGH for 1 1/2 minutes. Leave to cool.

Place the marshmallows and milk in a large bowl and cook on HIGH for 3 minutes, until melted, stir frequently. Leave to cool. Stir in the liqueur and refrigerate for 1 hour until mixture thickens, stirring occasionally.

Whip the cream until softly stiff and fold three quarters into the marshmallow mixture. Pour into the case and chill for at least 3 hours.

Decorate with remaining cream.

Timings are for a 600 watt microwave oven.