01 - Combine sliced beef with soy sauce, fish sauce, oyster sauce, sugar, minced garlic, and vegetable oil in a bowl. Mix thoroughly and let marinate for 15 minutes at room temperature.
02 - Cook rice vermicelli noodles according to package directions until tender. Drain well, rinse under cold running water to stop cooking and prevent sticking, and set aside.
03 - Whisk together fish sauce, lime juice, sugar, water, minced garlic, and minced chili in a small bowl until sugar completely dissolves. Taste and adjust balance as needed.
04 - Julienne cucumber and carrots into matchsticks. Rinse bean sprouts and drain well. Shred lettuce into bite-sized pieces. Keep all vegetables chilled until assembly.
05 - Heat a large skillet or wok over high heat until smoking. Add marinated beef in a single layer and stir-fry for 2-3 minutes until just cooked through and slightly caramelized. Remove immediately from heat.
06 - Divide vermicelli noodles among 4 serving bowls. Arrange lettuce, cucumber, carrots, and bean sprouts on top. Place sautéed beef over vegetables. Garnish with mint, cilantro, scallions, peanuts, and sliced chili.
07 - Drizzle nuoc cham dressing evenly over each bowl just before serving. Serve immediately while beef is still warm and vegetables retain their crisp texture.