Preheat the oven to 400 degrees F. Place the halibut in a parchment paper-lined baking dish. Drizzle fish with the oil; season with salt and pepper. Bake the fish 15 minutes, or until cooked through.
Meanwhile, place the remaining ingredients, except chopped cilantro and garnish, in a medium pot. Bring to a simmer over medium, medium-high heat. Simmer until the coconut milk had reduced by about a 1/3 and the sauce has lightly thickened. Mix in the chopped cilantro and reserve sauce on low heat.
When the fish is cooked, ladle a generous amount of the sauce in each of 4 shallow serving bowls. Set a piece of fish in each bowl, garnish with lime slices and cilantro sprigs, and serve.