Line 2 large baking trays with baking parchment. Melt the dark and white chocolate separately in heatproof bowls over pans of simmering water (don’t let the bottoms of the bowls touch the water).
Spoon teaspoonfuls of the melted chocolate onto the lined trays. Use the back of the spoon to spread the chocolate into discs about 5cm in diameter.
While the chocolate is still tacky, scatter the sprinkles, fruit and nuts and Black Forest mix over the top. Chill for 30 minutes to set. Keep in the fridge until needed.