1. Cook the udon noodles according to package instructions. Drain and set aside.
2. Heat the vegetable oil in a wok over medium-high heat. Add the garlic and ginger, and stir-fry for about 30 seconds.
3. Add the prawns and cook until they turn pink, about 2-3 minutes. Remove and set aside.
4. In the same wok, add the broccoli, carrots, and bell peppers. Stir-fry for about 5 minutes until they are tender-crisp.
5. Return the prawns to the wok. Add the cooked udon noodles, soy sauce, oyster sauce, and sesame oil. Toss everything together and cook for another 2-3 minutes until heated through.