In a small bowl mix the water cornstarch, soy sauce, and sherry, stir well and set aside.
In a wok or large skillet cook the gingerroot and garlic for 30 seconds in hot oil. Add half the thinly sliced pork and stir fry 3 minutes, until no longer pink. Remove, and add the remaining pork and cook until no longer pink. Return all the pork to skillet and add jicama, sweet peppers and green onion. Stir fry 1 minute more.
Stir in the slurry mixture and cook until bubbly and thickened.
Stir in the cabbage or spinach last and warm thru.