Toast 1-2 star anise pods, 2-3 cloves, 1 tablespoon cardamom pods, 1-2 cinnamon sticks, and 1 tablespoon coriander seeds in a frying pan on the stove.
Roughly chop 4 inches of fresh ginger and 1 large onion. Heat 2 tablespoons vegetable oil in the Instant Pot set to the saute program. Cook the ginger and onion for 2 to 3 minutes, stirring often.
Switch off the saute function and add the toasted spices to the pot. Stir for a few seconds, then add 2 pounds beef soup bones and 1 pound flank steak (or other lean beef, such as brisket or sirloin).
Fill with water not all of the way to, but just under, the max line. Close the lid and make sure the valve is set to the “sealing” position.
Set on manual high pressure for 45 to 90 minutes, depending on how concentrated you want the flavors of your broth to be.
When the broth is done cooking, remove the steak and slice it. Pass the broth through a sieve to remove the spices and any pieces from the beef bones.
Season the broth with 2 to 3 tablespoons fish sauce, 5 to 6 tablespoons of soy sauce, and 2 teaspoons brown sugar. Taste and season with salt as you like.
Dish the broth out into bowls and garnish with rice noodles, lime juice, beef slices, bean sprouts, basil, mint, scallions, and jalapeños as you prefer.