They're simple little things, the soft-shell crabs at Chez Thuy -- deep-fried whole, with a beautiful golden batter crisp out of the oil and just a little spicy, the shells inside chewy, yielding and full of juicy meat. The accompanying nuoc mam fish sauce is bright as acetylene, so sharp that a sniff of it is dizzying, like a toot of model-airplane glue. So you can be forgiven if you go a little nuts when the crabs (served two or three to an order) are brought to the table with a whole garden of sides: lettuce for wrapping, rice noodles, mint, basil, what-have-you. Dig in with your fingers and create the ideal bite: It just might be the best crab you'll ever eat in your life.