Soak the clams in lightly salted water with a clean nail for 2 hours to extract any sand. Scrub the shells and rinse well.
Heat a wok or large, heavy skillet over high heat until hot; add the oil, swirl, and heat for 30 seconds. Splash in the chopped garlic, ginger, scallions, and black beans, and stir rapidly until they exude their heavenly aromas. Add the clams and stir for 1 minute.