In a small bowl, whisk together the cornstarch, soy sauce, toasted sesame oil, oyster sauce, chicken broth, and light brown sugar until smooth. Set aside.
Heat a large skillet or wok over medium-high heat. Add a splash of toasted sesame oil, then add the sliced onion. Stir-fry for about 2-3 minutes until the onion is translucent. Add minced garlic and ginger paste, stirring for an additional minute until fragrant.
Toss in the frozen sugar snap pea stir-fry vegetables. Cook for about 5-7 minutes until the vegetables are heated through and tender-crisp.
Add the rotisserie chicken to the pan, stirring well to combine with the vegetables. Cook for another 2-3 minutes until the chicken is warmed through.
Stir the prepared sauce mixture into the skillet, ensuring all ingredients are coated evenly. Cook for an additional 2-3 minutes until the sauce thickens slightly.
Remove the skillet from heat and garnish with sliced green onions, sesame seeds, and a drizzle of Sriracha if desired. Serve hot over rice or noodles for a complete meal. Enjoy your delicious Rotisserie Chicken Stir-Fry!