Bring a pot of salted water to a boil. Cook noodles following the instructions on the package. Once cooked, drain and rinse under cold water for a few seconds to remove excess starch. Set aside.
Heat a nonstick pan on medium-high heat. Once the pan is very hot, add the oil, onion, mushroom, garlic, lemongrass, and ginger. Saute until the mushrooms start to brown and soften. Then add the beef and brown well until no longer pink while breaking it up into smaller pieces.
Stir the sesame oil, soy sauce, oyster sauce, and, bean sprouts. Bring to a simmer and reduce to concentrate the flavor. Adjust the seasoning with salt if needed then remove from the heat. Toss in the noodles and scallions.
Serve with bread. Garnish with chilis.