Rinse the chicken bones thoroughly. Boil them with a piece of ginger and the chicken leg or breast (use as much chicken meat as you like) for about 10–15 minutes until the chicken is cooked through. Remove the chicken and let it cool. Roast half an onion (with the skin on) until fragrant (you can skip this step if you prefer). Pour all the chicken broth into a pressure cooker along with the chicken pho broth cubes, roasted onion, and ginger. (Follow the instructions on the broth cubes for the amount of water to use.) Alternatively, you can simmer the broth first and add the cubes later.

Cook on the pressure setting for 15–20 minutes. Release the pressure, then remove all the bones, ginger, and onion, leaving only the broth. Taste and adjust seasoning with a little fish sauce for extra flavor.

Blanch the pho noodles before serving. Finely chop the scallions and culantro, thinly slice the onion, and shred or slice the chicken as you like. Place the noodles, scallions, culantro, and chicken in a bowl, then pour the hot broth over everything. Enjoy while hot. (If you find raw onion too strong, you can briefly dip it in the hot broth to soften it.)