Place thawed strawberries in blender container; blend until pureed. In large bowl, beat cream until soft peaks form. Add strawberry puree and condensed milk; stir gently to mix. Fold in chopped strawberries and walnuts. Fold in cake pieces.
Pour mixture into ungreased 13x9-inch (3-quart) glass baking dish; spread evenly. Cover with foil; refrigerate 8 hours or overnight. Garnish each serving with strawberry fan.