Add carrots, celery, onions, garlic, potatoes, and chicken the pot insert.
Next add black pepper, salt, and poultry seasoning followed by chicken broth.
Close the lid and set the valve to sealing.
Select the PRESSURE COOK button on HIGH PRESSURE and cook on manual for 8 minutes.
Once the pressure-cooking cycle is over, allow the pressure to release naturally for 5 minutes, then quick release the remaining pressure.
Carefully remove the chicken.
Shred the cooked chicken breast.
Melt butter in a saucepan.
Once melted add all-purpose flour, and mix to form a roux.
Set the instant pot on the SAUTE function.
Add the frozen peas and then add the milk. Stir to combine.
Add the shredded chicken back to the pot. Stir to combine.
Once the liquid starts to bubble add the roux to thicken the sauce. Mix and let simmer until the sauce thickens.
CANCEL the SAUTE button.
Serve hot with biscuits or bake in a pie crust.