In a bowl, whisk together the sesame oil, soy sauce, oyster sauce, dark soy sauce, chili garlic sauce, sugar, and white pepper. Set aside.
Bring a pot of water to a boil. Add the udon noodles and cook according to package instructions. Drain and set aside.
In a skillet over medium heat, add a splash of oil and sauté the garlic and ginger until fragrant.
Add the drained noodles and pour the sauce mixture over them. Toss everything together to coat the noodles well.
Cook for another 2-3 minutes until the noodles are evenly coated and heated through.
Top with sliced green onions and serve immediately.