In a small bowl, whip the heavy cream with a hand mixer 'til it forms soft peaks, about 2-3 minutes.
In a separate large bowl, mix together the mayo, lemon juice, sugar, salt, and pepper.
Gently fold the whipped cream into the dressing 'til the mixture is smooth and fluffy.
Fold the celery, grapes, walnuts, and apples into the dressing.
Cover and chill for 1-2 hours, or overnight if possible.
Serve on lettuce leaves, or with crackers and cheese.