My go-to at Mrs. Pho is item no. M5 but this would be the dish I'd have should I feel like having something different.
A classic from southern Vietnam, the "Hu Tieu Nam Vang" features skinny strands of slightly chewy tapioca noodles in clear pork broth. The toppings are prawns, lean pork and a hard-boiled quail's egg. As with most Vietnamese dishes, this too comes with an abundance of fresh herbs. I like this with the killer chilli paste that you can find on every table at Mrs. Pho's.