Oriental Shrimp Salad (Padma Lakshmi)

1 small onion , coarsely chopped

1 tablespoon minced gingerroot

12 black peppercorns , coarsely crushed

1 teaspoon ground cumin

1 teaspoon tamarind paste

1/2 teaspoon sugar

1/3 cup water

2 lbs large shrimp , shelled and de-veined

4 cups shredded iceberg lettuce

3 cups grated carrots

2 cups diced celery

2 cups shredded red cabbage

5 scallions , minced

1 cup loosely packed cilantro leaf , minced (after measuring)

3 tablespoons fresh limes or 3 tablespoons lemon juice

2 tablespoons oriental sesame oil

2 tablespoons soy sauce

1 tablespoon rice wine vinegar

3 dashes oriental hot chili oil (or to taste)

salt , to taste

vegetable oil cooking spray

3 tablespoons toasted sesame seeds , for garnish