Step 1

Freeze the flank steak until the meat is slightly frozen and firm enough to thinly slice with ease, 45 minutes to 1 hour.

Step 2

Finely grate 2 cloves of the 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.

Step 3

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 and up to overnight.

Step 4

About 30 minutes before finishing the dish, use tongs to transfer the steak to a large baking sheet lined with several layers of paper towels and arrange 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.

Step 5

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 large grinds of pepper in a medium bowl; set aside.

Step 6

Finely mince the remaining 2 cloves garlic and add to a small bowl. Finely mince the remaining ginger and add to the same bowl. Set aside.

Step 7

Heat 1 tablespoon of the canola oil in a large skillet over high heat. When the oil starts to shimmer, add a third of the steak strips in a single layer and cook until well-browned on the first side, about 1 minute. Flip and cook until browned on the second side, about 1 more minute. Transfer to a large plate. Cook the remaining steak in 2 additional batches, adding 1 1/2 teaspoons of canola oil per batch. Transfer to the plate.

Step 8

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.

Step 9

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 and toasted sesame seeds. Serve immediately with a side of steamed rice.