Step 1

Cut 1 pound skirt steak crosswise into 3 to 4-inch pieces. Cut each piece across the grain into 1/2-inch thick slices. Place in a medium bowl, season with 1/2 teaspoon kosher salt and 1/2 teaspoon black pepper, and toss to coat.

Step 2

Whisk 1/2 cup water, 3 tablespoons oyster sauce, 2 tablespoons soy sauce, 1 tablespoon plus 1 1/2 teaspoons packed dark brown sugar, and 1 tablespoon cornstarch together in a small bowl until the cornstarch is suspended.

Step 3

Heat 2 tablespoons of the canola oil in a wok or large frying pan over medium-high heat until shimmering. Add the steak in an even layer and cook undisturbed until browned on the bottom, 1 to 2 minutes. Flip the steak and cook until the second side is browned, about 1 minute more. Return to the bowl (the steak will not be cooked through).

Step 4

Drizzle the remaining 1 tablespoon canola oil into the pan. Add 1 thinly sliced medium yellow onion and 4 finely chopped garlic cloves. Stir-fry until the onion begins to brown, 2 to 3 minutes. Return the steak and any accumulated juices to the pan. Add 1 sliced large red bell pepper and 1 sliced large green bell pepper, and stir-fry until starting to soften, 2 to 3 minutes.

Step 5

Reduce the heat to medium. Whisk the cornstarch mixture again, then pour into the pan. Toss until combined. Cover and simmer until the sauce thickens and coats the meat and vegetables, about 2 minutes. Serve with cooked white rice.