1) Stem the raspberries and blueberries.
2) In a bowl, crush 1/2 cup of the raspberries.
3) Mix sugar with raspberries.
4) Allow to stand for 15 minutes and add in remaining berries.
5) Put a sponge layer on the serving plate.
6) Spread the sponge with about 1/3 of the ice cream and half of the berry mixture.
7) Place the remaining cake layer over the ice cream.
8) Spread the remaining ice cream and berries over the top sponge layer.
9) Place in the refrigerator until well chilled.