1. Line a 18cm springform pan with a double thickness of baking paper, ensuring that the paper is 10cm above the top of the pan. Spread an even layer of raspberries across the bottom of the pan and top with jam. Place ice cream in a bowl and soften with a wooden spoon. Chop half of the wagon wheels and stir into the ice cream with the mini marshmallows. Spoon ice cream mix over raspberries and smooth until flat. Cover and freeze for 2-4 hours until very firm.
2. Meanwhile for the Chocolate Butter, combine chocolate and butter in a microwave safe bowl. Microwave on medium power (50%) in 30 second bursts, stirring well in between, until chocolate and butter are melted and smooth. Cool in the fridge, stirring every 5-10 minutes to prevent the edges from setting, until thickened to a spreading consistency.
3. Remove ice cream from pan and discard paper. Place one of the cakes on the base of a serving plate. Top with ice cream layer and top with remaining cake. Spread chocolate butter over the top and the sides of the cake to cover. Return to freezer and allow to set for 30 minutes.
4. Heat cream in a saucepan to just below boiling point. Remove from heat and stir in dark chocolate until smooth. Stand for 5 minutes before drizzling over cake the top of the cake and creating dribbles down the sides. Decorate with fresh raspberries, mini wagon wheels and marshmallow skewers.