"B" ingredients: Combine the cornstarch, baking soda, and soy sauce in Ziploc bag. Add the steak, about a quarter at a time, mixing with the cornstarch mixture until well coated. (If necessary, you may have to double the cornstarch mixture, depending on the size of the steak.) Marinate for at least 1/2 hour.
Heat wok over high flame. Add 2 tablespoons peanut oil and stir fry beef till browned. Remove to serving bowl.
Do not wash wok. Add 1 tablespoon peanut oil to empty wok. Saute "A" ingredients till fragrant, about 1 minute.
Remove to serving bowl with beef.
Add last tablespoon oil to wok. Stir fry sugar snap peas, about 2 minutes. Add chicken broth, salt and pepper, and tomatoes. Simmer about 5 minutes.
Return beef to wok with the broth mixture, stir frying about a minute. If the sauce does not thicken combine the optional ingredients and add to wok, stirring about 1 minute or until thick. Add sherry and scallions. Stir for a few seconds to combine.
Serve with white rice.