Blacken/char the garlic, onion (cut side down) and ginger on the stove. You can place the ginger directly over the flame if desired, or in a pan.
Place the star anise, cinnamon and cloves in an 8-quart pressure cooker. Use the sauté function, toast for several minutes, stirring frequently, until fragrant. Add the charred garlic, onion and ginger. Stir and cook for a minute or two.
Add the bones, beef, fish sauce, salt, sugar and lime. Pour in 6 cups of water, more if needed. Just be sure not to go past the max fill line. Place the lid on and lock the lid. Cook on high pressure for 30 minutes. After cooking, allow pressure to decrease naturally, for about 15 to 20 minutes. When that is done, carefully open your pressure cooker.
Strain the broth into a pot through a fine mesh strainer lined with cheesecloth or muslin. Skim fat from the broth. You should have about 5 cups of broth.
Pour the broth back into your pressure cooker and immediately add the thinly sliced sirloin steak and rice noodles. Let cook for a few minutes. Alternatively, you can turn the instant pot ON to the saute function to bring the broth to a low boil and then add the the thinly sliced sirloin steak and rice noodles. Watch it as everything will cook very quickly. Ladle into bowls and serve the beef pho with the fresh garnishes, Sriracha and hoisin sauce if desired. Enjoy!