Thai Seafood Chowder

Name: Thai Seafood Chowder
Ingredients: 1 tablespoon vegetable oil; 2 shallots, thinly sliced; 2 cloves garlic, minced; 1 lemongrass stalk, finely chopped (or 1 tablespoon lemongrass paste — this stuff rocks, by the way); 2 cups chicken stock; 1 can (398mL) coconut milk; 1/4 teaspoon chili flakes (or a minced fresh chili if you can find one); 2 tablespoons rice vinegar; 1 tablespoon fish sauce; 1 tablespoon brown sugar; zest and juice of one lime; 3/4 pound snapper or other firm fish, cut into 1″ chunks; 1/2 pound prawns; 2 tablespoons basil, chiffonade