Clean and cut the beef into thin strips.
Season the beef strips with olive oil, light soy sauce, oyster sauce, and black pepper powder. Mix well and marinate for 15 minutes.
Cut the onion and bell pepper into strips.
Prepare a pot with water and bring to a boil.
Once it boils, cook the spaghetti and add a small amount of olive oil and salt.
Cook the spaghetti for 10 minutes and rinse with cold water afterward. Drain the water and set aside. Alternatively, cook the spaghetti according to the packaging instructions. Sometimes, I like to sample a small portion of the spaghetti to check its consistency after the 10-minute cooking time.
Prepare the sauce: mix light soy sauce, dark soy sauce, oyster sauce, starch, black pepper powder, and half a bowl of water.
Heat a pan with oil and stir-fry the marinated beef until it turns slightly brown.
Add chopped onions and bell peppers and continue stir-frying.
Mix in the cooked spaghetti.
Mix the sauce once more and drizzle it on top of the spaghetti. It is important to mix the sauce again since the starch tends to settle at the bottom.
Stir-fry and gently mix until the sauce thickens.
Adjust according to taste and sprinkle some black pepper powder if desired.