Whisk yogurt, mayonnaise, chutney, curry powder, salt and pepper in a large bowl.
Stir in tofu, celery, grapes, scallions and walnuts.
Cover and refrigerate for up to 2 days.
Note: I prefer water-packed tofu from the refrigerated section of the supermarket. Crumbling it into uneven pieces creates more surface area, improving the texture and avoiding the blocky look that turns many people away.