1. Slice pork thin against the grain. Dredge in cornstarch; then add soy sauce and toss.
2. Slice ginger root thin. Cut scallion in 1/2-inch sections.
3. Heat oil. Add pork and stir-fry until it loses its pinkness (about 2 minutes). 4. Add ginger root and scallion; stir-fry a few times. Then add water and sugar and cook, covered, until done (about 3 to 4 minutes). Serve at once.