SCRUB THE MUSSELS UNDER COLD water and pull off the wirelike beards. Soak in a large bowl in several changes of cold water. Drain thoroughly just before cooking. Heat a wok or skillet until hot; add oil. Add garlic, ginger and black beans; stir-fry 30 seconds. Add bean sauce and chili bean sauce and stir-fry for another 10 seconds. Add mussels and stir-fry for 1 minute. Add rice wine, soy sauce and stock. Cook over high heat until the shells are completely open. Discard unopened mussels. Garnish with the chopped scallions and serve immediately.