Stir boiling water into gelatin in a large bowl for at least 2 minutes until completely dissolved. Stir in the pineapple and juice. Refrigerate 1-1/4 hours or until it reaches the consistency of unbeaten egg whites.

Whip the cream. Stir the cottage cheese into cream cheese in separate bowl until well blended. Gently fold in the whipped cream until smooth. Beat into slightly thickened gelatin with a wire whisk until well blended. Stir in walnuts and marshmallows. Pour into a 6-cup mold sprayed with nonstick cooking spray.

Refrigerate 4 hours or until firm. Unmold. Surround with lettuce leaves, if desired. Store leftover salad in refrigerator.