Season the flank steak with 1 teaspoon of salt and half a teaspoon of pepper. Add 1 teaspoon of chopped shallot. All are mixed well and left for about 20 minutes.
In a pan, fry cinnamon sticks and star anise until fragrant.
Place the onion slices on a baking sheet. Broil in the oven until charred. This adds depth of flavor to the broth.
In a large pot, add vegetable oil and the remaining shallots, saute it for a few minutes. Add flank steaks and stir continuously for about 5 minutes or until the meat is firm.
Add water, 2 slices of crushed ginger, the charred onion, cinnamon sticks, and star anise to the pot. Bring to a boil and then let it simmer for at least 30 minutes to allow the flavors to meld.
Add fish sauce, soy sauce, 1 tbsp of MSG, salt, and pepper to the broth. Adjust the seasoning according to your taste.
While making the broth, cook the rice noodles according to package instructions. Rinse with cold water and set aside.
Divide the cooked rice noodles among serving bowls. Top with green onions and bean sprouts. Ladle the hot broth over the noodles.
Top the bowls with fresh herbs like cilantro, basil, and mint. Serve lime wedges, chili or tomato sauce on the side.