Step 1Heat a wok over medium heat until hot. Add the oil, then the garlic and onion, and cook, stirring frequently, until fragrant and beginning to brown. Add the chiles and continue to stir-fry until the chiles are softened and everything is well-browned, 8 to 10 minutes. Stir in a tablespoon of chile powder to taste for added heat, if desired. Remove from heat and place in a large mortar. Pound with a pestle until the mixture is reduced to a paste, 10 to 15 minutes. The paste can also be made using a food processor or blender, but the flavor is best using a mortar and pestle. Set the paste aside.
Step 1Heat a grill or grill pan over medium heat until hot. Season the fish with a light sprinkling each of chile powder, fish sauce and lime juice. Wrap the fish in foil and place on the grill (if using a pan, cover the pan with an inverted roasting pan to contain the heat. Grill until the skin peels away easily and the flesh is firm and opaque, 10 to 15 minutes, depending on the size of the fish. Remove from heat, skin the fish and separate the meat from the bones, checking to make sure any small bones are removed. Place the meat in a large mortar, and, using the pestle, pound the meat until it is ground.
Step 1Cook the cabbage in a small pot of simmering water until softened, about 5 minutes. Drain well and set aside.
Step 1Heat a wok over medium heat until hot. Add the oil, and when it begins to shimmer, add 1/3 of the chile paste. Stir-fry the paste until fragrant and the paste begins to brown, 2 to 3 minutes. Add the ground fish and continue to cook, stirring frequently to marry the flavors. Continue to cook for several more minutes, tasting frequently, and continuing to flavor as the fish dip cooks: fish sauce will help to season the dish as if using salt, lime juice will brighten the dish and add a hint of sour flavor, a touch of sugar will sweeten with notes of caramel, and additional chile paste will add more heat.
Step 2Remove from heat and place the dip in a serving bowl.
Step 3On a large plate or small platter, arrange the condiments: wedges of fresh and boiled cabbage, lettuce leaves, chiles, cilantro and basil, sliced cucumber, bell pepper and lime wedges. Serve the condiments alongside the dip.