Grease 4 (8-oz.) ramekins with oil and divide the fish evenly in 4 ramekins.
In a large bowl, whisk the coconut milk with the curry paste, chili-garlic paste, fish sauce, palm sugar, salt and eggs, until smooth. Divide the custard evenly in the ramekins. Alternatively, fashion banana leaves into boats, fasten the edges with toothpicks and use in place of the ramekins.
If steaming: Pour about 2 inches of water in a steamer and place the ramekins inside. Steam until the custards are set, but jiggle slightly in the center, about 20 minutes.
If roasting: Heat the oven to 350 degrees and place the bowls inside a roasting pan. Place the pan inside the oven and pour enough boiling water in the pan to come halfway up the sides of the bowls. Bake until the custards are set, but jiggle slightly in the center, about 50 minutes. Lift the bowls from the water bath and set on a plate. Garnish with the lime leaves and red chiles.
Note: If you don't want to take the time to make your own rice crackers, you can easily substitute store-bought rice cakes. Canned coconut milk is best bought at Asian grocery stores, which has varieties that are typically much creamier than Western types. If tamarind paste is unavailable, dried tamarind can be ground into a paste by hand. If you don't have a mortar and pestle, substitute a small bowl and a wooden spoon. Palm sugar is commonly found at Asian groceries; however, brown sugar can be substituted if necessary. Prawn tomalley (the orangish-red substance visible in whole prawns' heads) can be extracted easily from prawns themselves — however, to collect the amount necessary for this recipe, about twice the amount of shrimp called for will be required. Use the leftover shrimp for another dish or substitute for the fish in the amok recipe. To extract the tomalley, pull off the outer shell of the prawn heads and squeeze the red paste-like substance into a small bowl. The tomalley lends a pungent, fishy flavor to the dish but can be omitted if necessary. From "Bangkok: Recipes and Stories From the Heart of Thailand," by Leela Punyaratabandhu.