Combine all the broth ingredients and 7 cups water in the Instant Pot on the Soup setting for 30 minutes. If cooking stove top then bring to a boil and simmer for an hour.
Skim any dark residue off the top and strain the stock
Shred the chicken when it is cool enough to handle and set aside
Pour the broth into a pot (or back into your IP)
Bruise the bottom of the lemongrass stalks to get the flavour going, cut into big chunks
Add the lemongrass to the pot and bring to a boil
Now add the rice and simmer till it's done, about 15 minutes
Mix the salt, pepper and juice of half a lime in the pot, taste, adjust seasoning if needed
Stir in the shredded chicken, cilantro, chillies and scallions.