For the coconut sauce: Place a large skillet over medium-high heat and add the oil. When it is hot, add the ginger and onions
and cook until golden, 3 to 5 minutes. Add the curry leaves
, coriander seeds and green chili and cook for 30 seconds. Add the coconut milk, turn the heat down to low and continue to cook until the sauce
has thickened, 3 to 5 minutes. Taste for seasoning and add salt as needed. Keep warm.
For the halibut: Place a large nonstick skillet over medium-high heat and add the oil. Sprinkle the halibut with the coriander, cumin
, salt and pepper and place them in the pan. Cook on one side for 4 minutes, and then turn the heat down and continue to cook until they are done, 3 to 4 minutes. Keep warm.
For the peas: Place a small skillet over medium-high heat and add the butter. When it begins to foam
, add the mustard seeds
and cook until they begin to pop, about 1 minute. Add the peas and saute until they are bright green and tender-crisp, 3 to 5 minutes. Season with salt and pepper.
To serve: Ladle some coconut sauce on each of 4 plates. Place a halibut fillet over it and garnish