Slice cake crosswise into three equal layers.
Combine sour cream, sugar and crushed strawberries.
Fold sliced strawberries, 3/4 cup of the bananas and sour cream mixture into whipped cream; chill 30 minutes or until mixture starts to thicken.
Spread about 1/2 cup fruit mixture on each layer, including top of cake; stack layers.
To serve, garnish top of cake with remaining banana slices and strawberry halves.
Cut into wedges with electric knife.