Heat the oil in a wok or heavy-based frying pan, swirling gently to coat the base and sides. Add the garlic and cook, stirring, until pale gold. Add the prawns (shrimp) and pork, and stir for 3 minutes, or until the prawns (shrimp) are pink. Add the noodles to the wok/skillet with the black bean sauce, soy sauce, vinegar, and stock. Stir-fry over high heat until the mixture has heated through and the sauce has been absorbed.