Ingredients

1 1/2 pounds boneless, skinless chicken breasts, halved horizontally and thinly sliced (see Cook’s Note)

Coarse salt and ground pepper

2 tablespoons olive oil

1 large onion, halved and thinly sliced

1 large red bell pepper, ribs and seeds removed, thinly sliced

3 cloves garlic, minced

1 1/2 teaspoons grated peeled fresh ginger

1/4 to 1/2 teaspoon red-pepper flakes

3 tablespoons soy sauce

3 tablespoons rice vinegar

1 1/2 teaspoons cornstarch, mixed with 1 tablespoon water

12 to 16 Boston lettuce leaves (about 2 heads)

Preparation

Season chicken with salt and pepper. In a large nonstick skillet, heat 1 tablespoon oil over high heat. Add half the chicken; cook, stirring constantly, until opaque throughout, 2 to 4 minutes. Transfer to a plate. Repeat with remaining chicken.

Add remaining tablespoon oil to pan, along with the onion and bell pepper. Cook, stirring constantly, until onion is tender and golden, about 4 minutes (reduce heat if browning too quickly).

Reduce heat to medium; add garlic, ginger, and red-pepper flakes; cook, stirring, until fragrant, 30 to 60 seconds.

Stir in soy sauce, vinegar, and cornstarch mixture; remove from heat. Add chicken and any accumulated juices; toss to coat. Serve in lettuce cups.