Line a 3cm-deep, 26cm x 16cm (base size) slice pan with baking paper, allowing the 2 long sides to overhang. Arrange 11 biscuits in a single layer over the base of the prepared pan, chocolate-side up, cutting the final biscuit in half to fit.
Use electric beaters to beat cream and condensed milk in a bowl until soft peaks form. Fold in raspberries until just combined. Pour mixture over biscuit base and smooth the surface. Arrange remaining biscuits on top, chocolate-side down, cutting the final biscuit in half to fit. Cover and place in the freezer for 8 hours, or overnight, until firm.
Remove the slice from the pan using the overhanging paper. Cut around the biscuits into bars to serve.
