1. Slice pork thin against the grain, then cut in strips. Peel carrots and cut in strips, then parboil. Remove tough spinach stems; cut leaves in half. Mince scallion. Blend cornstarch and cold water to a paste.
2. Heat oil. Add scallion and stir-fry until translucent. Add pork and stir-fry until it begins to brown.
3. Add carrots and soy sauce. Stir-fry 1 minute.
4. Add saIt, then spinach and stir-fry until it begins to soften (about 1/2 minute). Then stir in cornstarch paste to thicken. Serve at once.