1.Spray a baking sheet with oil and add onion wedges from 2 onions and ginger. Spread out into a single layer. Place the sheet tray in the oven about 6 inches from the element and start the broiler. Broil until ingredients are slightly charred about 5 minutes, monitoring the whole time then remove and set aside.
2.Add beef shanks to a pot with 6 cups of water or enough to cover them. Then, turn the heat on high and bring it up to a boil. Once boiling turn it down then let it continue to simmer for 7 minutes. Discard water and wash all scum from the shanks.
3.Add the star anise, coriander seeds, fennel seeds, cloves, and cinnamon stick to the instant pot insert and toast them on the high sauté setting until fragrant, about 3 minutes.
4.Return beef shanks to the pot along with charred ginger and onions, fish sauce, sugar, salt, and 10 cups of water. Cook at high pressure for 30 minutes. Allow pressure to release naturally for at least 60 minutes.
5.Pour the broth through a fine mesh strainer into a large pot. Separate the beef shank and shred, then discard the other strained ingredients.
6.Place the pot on the stove and bring it back to a boil. Meanwhile, in another pot cook rice noodles according to package instructions then rice the noodles and place in each soup bowl.
7.Divide beef slices and shank meat among bowls and top with sliced onions, cilantro, and green onions. Pour boiling broth over the steak to cook it. Top with lime wedges, Thai Basil, jalapenos, and bean sprouts and serve immediately. Serve with hoisin sauce and sriracha on the side.