Cook the noodles according to package directions, then drain and set aside.
In a bowl, toss chicken slices with cornstarch and 1 tbsp soy sauce until coated.
Heat vegetable oil in a large pan and cook chicken until golden, then remove and set aside.
In the same pan, add garlic and sesame oil, cooking until fragrant.
Stir in remaining soy sauce, oyster sauce, brown sugar, and chicken broth. Let it simmer until slightly thick.
Return chicken to the pan and toss with sauce until sticky.
Add noodles and toss everything together until coated.
Top with green onion and chili flakes before serving.