Cook green beans in boiling water 5 minutes, and drain. Blend 1/4 cup water, hoisin, cornstarch, and cayenne pepper. Heat vegetable oil in a large nonstick skillet over medium-high heat. Add 1/2 cup scallions and ginger; sauté 30 seconds. Brown pork. Add tofu, and sauté 1 minute. Add hoisin mixture and beans, and cook for 30 seconds. Stir in 1/4 cup scallions, sesame oil, and salt. Serve with rice.