1. Place the biscuits in a large plastic food bag and roll with a rolling pin to crush finely. Mix with the icing sugar in a large bowl. Melt the dark chocolate with the butter over a gentle heat then add to the biscuits with 50g of the honeycomb pieces and mix thoroughly. Press firmly into a buttered 20 x 26cm swiss roll tin lined with baking parchment. Chill for 15 minutes until set.
2. Melt the milk chocolate in a basin set over a pan of simmering water (don't let the basin touch the water). Spread over the biscuit base and arrange the raspberries over the top, pressing them lightly into the chocolate. Scatter with the remaining honeycomb pieces. Chill until the chocolate has set then cut into squares. This cake improves with keeping for a day as the flavours develop.
Recipe courtesy of Waitrose