Cook the spaghetti according to package instructions. Drain and set aside.
Heat 1 tbsp oil in a large pan over medium-high heat. Add chicken slices and cook until browned and cooked through. Remove from pan and set aside.
In the same pan, add the remaining oil and sauté garlic, bell pepper, and carrot for 2-3 minutes until tender.
In a small bowl, mix soy sauce, oyster sauce, sesame oil, chicken broth, and cornstarch.
Return the chicken to the pan, add the cooked spaghetti, and pour in the sauce mixture.
Stir well and cook for another 2 minutes until everything is well coated and heated through.
Garnish with green onions and sesame seeds before serving.