Line a 8 inch square baking tin with baking paper, making sure the edges overhang slightly so the rocky road is easy to lift out once set.
Break the biscuits into medium-sized chunks and place them in a large mixing bowl. Add the mini marshmallows and chopped sponge cake pieces, then gently mix together.
Melt the white chocolate gently over a pan of simmering water or in short bursts in the microwave, stirring until smooth and fully melted.
Pour the melted chocolate mixture over the biscuit, marshmallow, and sponge mixture. Stir gently until everything is evenly coated in chocolate.
Spoon the rocky road mixture into the lined tin and press it down gently with the back of a spoon to create an even layer.
Melt the topping white chocolate gently over a pan of simmering water or in short bursts in the microwave, stirring until smooth and fully melted.
Pour the chocolate mixture over your rocky road and spread it out evenly. Swirl a little extra jam on top or decorate with extra biscuit pieces!
Place the tray in the fridge and chill for 2–3 hours, or until the rocky road is fully set.
Once set, remove from the tin, slice into squares or bars.
