Wash green beans and trim into bite sized pieces. Steam or microwave with a little water until just tender-crisp. Drain and rinse with cold water to stop cooking.
Mix together the black bean paste, soy sauce, water and corn starch until very smooth.
Heat a wok or large saucepan to medium high. Add some water and the cooked beans. When beans are heated (about 2 minutes) add the sauce. Stir constantly to coat the beans (sauce will get very thick). Serve immediately over hot cooked rice.