Cut asparagus on a diagonal into 2" pieces. Cut steak lengthwise into 3" wide strips and cut strips crosswise into 1/4" slices. In a bowl, toss steak with soy sauce, sherry and cornstarch. Rinse black beans to remove excess salt. In a small bowl, mash black beans with garlic and 2 teaspoons oil. In a wok, heat remaining oil over medium heat. Add asparagus and stir fry until tender but still crisp, about 3 minutes. With a slotted spoon, remove to a plate. Return wok to high heat until smoking. Add ginger, scallions, and black bean mixture. Stir fry until aromatic, about 30 seconds. Add beef and cook until browned around the edges but still pink inside, 2-3 minutes. Add stock, oyster sauce, sugar, and asparagus. Stir fry over high heat until sauce is hot and blended, about 1 minute. Remove from heat. Sprinkle with sesame oil and serve.