This was a regular meal in our house back in the day. It used to be one of my favorites - and it was something mom used to be able to throw together pretty quickly. Since I've started making it I realize it's very forgiving as well - it's pretty hard to mess up. You don't have to carefully measure in all the ingredients. After all, mom never bothered to measure anything. I don't think I've ever consistently put the same quantity of ingredients in there either.
When I was a little girl living in Misawa Air Force Base, Japan, there was a little Chinese restaurant near the main gate. You would go there and order a set meal, and it came with so many different courses and each tasted better than the one before. One of the items I believe was this dish. To this day I think that was the best Chinese food I've ever had. That's saying something because generally speaking, Chinese food in Japan is pretty bad. Except this place, which beats anything I've ever had here in the US.
Just a couple of things to note -
Cut the beef into half inch long thin strips.
Combine marinade ingredients in a shallow bowl. (2 teaspons soy sauce, 2 teaspoons sake, 1 teaspoon sesame oil, 1 teaspoon corn starch, ginger and garlic)
Add sliced beef to the marinade, stir and cover. Keep in refrigerator from 30 minutes to overnight, depending on the toughness of the beef.
Remove seeds from the bell pepper and cut into bite sized strips.
In a small bowl, whisk together sauce ingredients. (1.5 tablespoon soy sauce, 1 tablespoon sake, 2 tablespoons chicken broth, 1 teaspoon sesame oil, 1 teaspoon sugar, 1 teaspoon corn starch)
Preheat cast iron pan with one teaspoon of vegetable oil.
Add bell peppers to the pan and sautè until they are mostly cooked through but still slightly firm. Remove bell peppers and set aside.
Add more oil to the pan if needed, and add beef to the pan. (If cooking in cast iron pan will always need a slight coating of oil to prevent sticking).
Sautè beef in pan until mostly cooked through but still slightly pink.
Add green peppers to the pan and stir until beef and bell peppers are completely cooked.
Whisk sauce mixture to break up any congealed corn starch. Pour into pan and mix everything together.
Sauce will thicken quickly. Remove from heat and serve.