Soak the tamarind in 1/2 cup of hot water for 10 minutes. Strain and reserve the liquid.
Heat 1 tablespoon of oil in a pan and add the mustard seeds and cumin seeds. When they start to pop add curry leaves and fry for few seconds. Then add the onions, garlic & peppercorns. When they are soft, mix the coconut milk, tamarind liquid, red chili powder, turmeric powder & salt. Cover & cook for 10 minutes over medium low heat. Now add the shrimp & simmer cook until they are cooked.