Step 1Combine chicken and 1/4 cup cornstarch in a large bowl and toss to coat. Heat vegetable oil in a large skillet over high heat. Fry chicken until cooked through and golden, 4 to 6 minutes. Add green onions and peppers to skillet and cook until tender,2 to 3 minutes more, then transfer chicken and vegetables to a large plate.

Step 2Clean skillet and reheat over medium-high heat. Add 2 teaspoons sesame oil, ginger, chilis, and garlic, and cook until fragrant, about 1 minute. Stir in soy sauce and brown sugar until sugar is dissolved. In a medium bowl, whisk to combine 1/2 cup water with remaining cornstarch until smooth. Add this mixture to sauce and stir to combine. Let simmer 2 minutes, or until sauce has thickened slightly.

Step 3Return chicken to pan and stir to coat in sauce, then remove from heat. In a medium bowl, mix rice noodles with rice vinegar and remaining 1 teaspoon sesame oil.

Step 4Place a bit of rice noodles into each lettuce cup and top with carrots and chicken. Garnish with green onions before serving.