Beef with Scallions, Tomato, and Ginger

Ingredients

• 4 servings rice steamed for serving
• 1.5 teaspoons cornstarch 
• 2 teaspoons sesame oil dark
• 2 tablespoons cooking sherry dry
• 1 pound flank steak very cold (See Cook's Note.)
• 2 inch ginger fresh peeled chopped (preferably young ginger) (See Cook's Note.)
• 1 tablespoon hoisin sauce mixed with 1 tablespoon water
• 1 bunch scallions cut into 2-inch long pieces, whites and greens kept separate
• 2 tablespoons soya sauce 
• 1 teaspoon sugar 
• 1 pound tomatoes ripe cut into large chunks (into 8ths) ( 3 to 4 medium tomatoes)
• 2 tablespoons vegetable oil 

Equipment

• bowl
• frying pan
• whisk

Directions

1. Cut the beef against the grain into thin strips about 2 inches long (by 1/4-inch thick). In a large bowl, whisk together the sherry, soy sauce, sesame oil, cornstarch, and sugar.
2. Add the beef and mix well. Set aside.
3. Preheat a large non-stick skillet over high heat.
4. Add 1 tablespoon of the oil and heat until very hot.
5. Add the scallion whites and beef mixture to the skillet, arrange it in a single layer, and cook, without stirring, until well-browned on the bottom and still pinkish inside, about 1 minute. (It is key to only partially cook the meat at this stage, since it will be finish cooking later in the sauce.)
6. Transfer to a bowl.
7. Return the skillet to the heat and add the remaining oil.
8. Add the ginger and cook, stirring, until fragrant, about 30 seconds to 1 minute (only a few seconds if using young ginger).
9. Add the scallion greens and tomatoes and cook until slightly softened and saucy, and tomato skin begins to wrinkle, about 1 minute. Return the beef and any collected juice to the skillet, add the hoisin sauce, and cook, stirring, until thick, about 30 seconds more. Season, to taste.
10. Transfer to a serving platter and serve immediately with rice.