Combine beef with garlic, sesame oil, salt, pepper and oyster sauce and set aside for at least 30 minutes.
Follow package instructions to cook vermicelli noodles, then strain in a colander, rinse under cold water, and set aside at room temperature.
(Sauce) Stir the sugar and water together to melt the sugar, then add in the garlic, lime juice, fish sauce, rice wine vinegar, chili and carrots.
Heat sesame oil in a large skillet and stir-fry the onions til translucent, then stir-fry beef in batches until browned + cooked through.
Divide the vermicelli noodles into each bowl and top with cucumbers, carrots, and lettuce.
Add the cooked beef to each bowl and top with cilantro, mint, toasted peanuts and crispy shallots.
Drizzle with the nuoc cham sauce and serve!