Parboil the beef bones and beef shank for about 5–10 minutes. Drain, rinse, and clean them well to remove impurities.
Char the onion and ginger until nicely blackened on all sides.
Toast the pho spices in a dry pan until fragrant, then place them into a spice bag.
Add the beef bones, beef shank, charred onion, ginger, and spice bag into the Instant Pot.
Fill with water up to the max line. Add fish sauce and rock sugar.
Cook on High Pressure for 1 hour, then allow natural release if possible.
While the broth cooks, prepare pho noodles according to package instructions and chop your toppings.
Strain the broth into another pot. Add more water if needed, then season with salt and additional fish sauce to taste. Bring to a boil again.
Add pho noodles, sliced beef shank, raw thinly sliced beef, cilantro, and green onions to your bowl.
Pour the hot broth over everything to cook the raw beef. Finish with a squeeze of lime — and enjoy!
