Marinate Chicken: In a medium bowl, whisk together soy sauce, brown sugar, minced garlic, grated ginger, sesame oil, black pepper, and optional chili flakes until the sugar is dissolved. Slice the chicken into thin strips, add it to the marinade, and ensure it’s well coated. Let the chicken marinate for at least 20 minutes.

Heat the Skillet: Preheat a large skillet or non-stick pan over medium-high heat. Lightly coat the skillet with a drizzle of oil and heat until shimmering.

Cook Chicken: Add the marinated chicken strips in a single layer and cook for about 5 to 7 minutes, until fully cooked through and golden-brown.

Garnish and Serve: Transfer the cooked chicken to a serving platter. Garnish with chopped green onions and toasted sesame seeds. Serve immediately with rice or in lettuce wraps.