In a small bowl, combine oyster sauce, Hoison sauce, dark and light soy sauce, sugar and warm water. Mix until the sugar is fully dissolved then add in minced ginger and garlic. Mix until fully combined then set aside.
For the beef
Thinly cut beef against the grain into 1/4" strips.
Heat 1/2 cup of oil in a wok or large pan over medium high heat. Shallow fry the beef for about 3 minutes on both sides. Remove beef from the oil and drain the excess oil, leaving about 1 tbsp.
Sautè onions, white part of the green onion, red peppers and chili peppers in rendered beef fat until the onions begin to soften. Add in green onions and minced garlic. Sautè until the garlic is fragrant. about 2 minutes.
Add in Udon noodles and pour in the sauce and water. Slowly break the udon then toss until it's coated. Return beef back into the pan. Add in more green onions and toss until the sauce covers the beef, noodles and veggies.
Add a little more dark soy sauce for color, if needed. Toss together.
Top with sesame seeds, green onions and Sriracha if desired and enjoy!