Put shrimp in a medium bowl, and season with salt.
Heat oil in a wide skillet over medium-high heat. Add Serrano chile, garlic and ginger. Saute 2-3 minutes. Add tomato paste, tamarind and spices. Cook a few minutes until spices become fragrant. Add mushrooms and stir for about 2 minutes. Add shrimp and cook, stirring for about 2 to 3 more minutes until shrimp have turned pink and mushrooms have softened.
Add coconut milk and simmer for about 3 minutes. Taste sauce and adjust seasoning. Transfer to a serving dish.
Garnish with cilantro and serve with either basmati rice, chapati or naan.