1 pound flank steak or you can purchase stir-fried steak at your grocery store that is sliced and recipe ready
4 cloves garlic
One 1-inch piece of ginger
7 tablespoons ow-sodium soy sauce
1/4 cup Shaoxing wine or dry sherry
1 tablespoon brown sugar
Freshly ground black pepper
½ cup beef broth
2 teaspoons toasted sesame oil
2 tablespoons peanut oil
1 medium white onion, cut into 1-inch pieces
1 large red bell pepper (about 8 ounces), cut into 1-inch pieces
1 large green bell pepper (about 8 ounces), cut into 1-inch pieces
1 ½ tablespoons cornstarch
2 sliced scallions
Cooked Jasmine or white rice, for serving
If using flank steak: Freeze the flank steak until the meat is slightly frozen and firm enough to thinly slice with ease, 45 minutes to 1 hour.
Grate 2 cloves of garlic into a large bowl. Peel the ginger and cut it in half. Finely grate one of the ginger halves into the same bowl; reserve the remaining ginger. Whisk in 3 tablespoons of the soy sauce, 2 tablespoons of the Shaoxing wine, 1 1/2 teaspoons of the sugar, and several large grinds of pepper to combine. Set aside.
Thinly slice the flank steak against the grain on a very slight bias into 1/4-inch-thick strips. Cut any extra-long pieces in half; the strips should be no longer than 3 to 4 inches. Add to the bowl with the marinade and stir to combine. Cover with plastic wrap or a lid and refrigerate for at least 1 hour or overnight.
When ready to cook use tongs to transfer the steak to a large baking sheet lined with several layers of paper towels and arrange it in a single layer. Lay additional paper towels on top to help absorb any excess marinade. Set aside to take the chill off the meat.
Whisk together the beef broth, sesame oil, remaining 1/4 cup soy sauce, remaining 2 tablespoons Shaoxing wine, remaining 1 1/2 teaspoons sugar, and a couple of large grinds of pepper in a medium bowl; set aside.
Finely mince the remaining 2 cloves of garlic and add to a small bowl. Finely mince the remaining ginger and add to the same bowl. Set aside.
Heat 1 tablespoon of the peanut oil in a large skillet over high heat. When the oil starts to shimmer, add half of the steak strips in a single layer and cook until well-browned on the first side, about 1 minute. Turn over and cook until browned on the second side, about 1 more minute. Transfer to a large plate. Cook the remaining steak adding 1 1/2 teaspoons of oil per batch. Transfer to the plate.
Lower the heat to medium-high. Add the onion and a splash of water to the empty skillet and cook, scraping up any browned bits and stirring constantly, for 2 minutes.
Add the red and green bell peppers and cook, stirring frequently and adding another splash of water if the skillet starts to get too brown on the bottom until the vegetables are crisp-tender, 5 to 7 minutes.
Add the garlic and ginger and cook, stirring constantly, until softened about 1 minute.
Return the steak to the skillet and stir to combine. Whisk the cornstarch into the sauce, then pour it into the skillet. Cook, stirring constantly, until the sauce is thick and glossy, about 2 minutes. Transfer the pepper steak to a large serving platter and top with sliced scallions Serve immediately with a side of rice.