Gently rinse and pat dry scallops. Season with salt and pepper.
Add coconut milk, ½ of the lime zest (save the rest for garnish) the smashed lemongrass and the ginger, and simmer gently on medium low heat for 5 minutes. Do not over boil. Stir in 1 ½ teaspoons fish sauce and 1 tablespoon lime juice, turn the heat off and taste. Adjust with more lime or fish sauce if you want. Add a few slices of fresh red chili for heat. Set aside and let flavors infuse while the rice is cooking.
In a small sauce pan, simmer shallot in vinegar on low heat, until vinegar reduces almost completely, about 5 minutes.