Char the aromatics

• Char the halved onion, halved ginger and carrot pieces on a hot grill until nicely blackened.
• Set aside.

Build the broth

• Put the rotisserie chicken bones in a large stockpot with the water.
• Add the fish sauce, rock sugar, chicken pho soup base and the pho spice bag.
• Add the charred onion, ginger and carrots along with the chopped celery.

Simmer the broth

• Bring to a boil, then lower the heat and simmer gently, skimming the surface.
• Cook until the broth is deeply flavored and slightly reduced.

Season and add the chicken

• Remove the spice bag and bones, then taste and adjust the seasoning.
• Stir in the shredded rotisserie chicken and heat through.

Serve

• Ladle the hot broth and chicken over noodles in bowls.
• Top with scallions, cilantro, sliced white and red onion and bean sprouts.
• Serve with lime wedges and fried garlic chili oil on the side.