Char 1 onion, 3-4 shallots, cinnamon stick, and star anise until fragrant. Toast half a packet of dried pho spices, then place all the spices, cinnamon, and star anise in a cloth bag and tie it closed. Rinse the chicken with salt and white wine to remove odors, then let it drain.

Bring 12-16 cups (3-4 liters) of water to a boil with the spice bag. Once boiling, add the charred shallots and onion along with the chicken (leave the half chicken whole). Bring to a boil, then reduce heat and simmer for 30-40 minutes. When the chicken is just cooked through, remove it and briefly dip it in cold water or cool it in front of a fan to firm up the skin. Cut the duck blood pudding into bite-sized pieces and add to the pot, simmering for another 15 minutes.

Season the broth with chicken bouillon, sugar, MSG, and salt to taste. Make it slightly stronger in flavor so it balances with the noodles. Shred the chicken into bite-sized pieces. Finely chop scallions and a little culantro. Slice the onion thinly. You can set aside the white parts of the scallions to briefly blanch with the bean sprouts.