For the cream sauce:
In a bowl, Put all the ingredients for the sauce with little water except coconut milk and mix well. Then slowly add the coconut milk and mix everything together. Set aside.
Heat the oil in a pan and add mustard seeds. When they begin to pop add garlic and curry leaves and fry for few seconds. Then add the shrimp and stir-fry until the shrimp is almost cooked over medium high heat. Now add the sauce. Let the sauce simmer over medium heat until the shrimp is completely cooked. Remove from heat and serve hot with rice.