Heat sesame oil in a large pot over medium heat. And onion, garlic and ginger. Sauté 3 minutes. Add cabbage and mushrooms and continue to cook 5 minutes longer.
While vegetables cook, boil ramen noodles per package directions. Strain and set aside.
Add chicken broth, oyster sauce, soy sauce, and rice vinegar into vegetable mixture and bring to a boil. Reduce heat to simmer and add shredded chicken. Stir well. Simmer 10 minutes. Divide ramen noodles among serving bowls. Ladle soup on top and garnish with desired toppings.