Line a 20cm x 30cm slice pan with baking paper, extending paper over rim of pan.
Using a food processor, process the biscuits into fine crumbs. Add the melted butter and process until just combined. Press biscuit mixture evenly over base of prepared pan. Refrigerate for 10 minutes.
Place the raspberries in a bowl. Using a fork, crush the raspberries. Stir in the jam until combined. Spread the jam mixture over the biscuit base.
Place the marshmallows and milk in a saucepan over medium-low heat. Cook, stirring, for 5 minutes or until marshmallows have melted and mixture is smooth. Remove from the heat and immediately pour over the jam layer, spreading with a spatula to level. Refrigerate for 3 hours or until set.
Place the chocolate and oil into a microwave-safe bowl. Melt in the microwave on medium-high for 30 seconds. Stir and cook for a further 20-30 seconds or until melted. Spread the melted chocolate over the marshmallow. Refrigerate for 30 minutes or until chocolate is set. Serve cut into squares.
