Whisk together all ingredients (except the chicken) in a pot until combined. Add the chicken and cover with a lid. Bring to a simmer on medium heat until the chicken reaches an internal temperature of 160°F using a thermometer.
Remove the chicken, using 2 forks pull the chicken apart to shred. Return the chicken to the pot and bring back to a simmer until the sauce reduces and thickens. Adjust the seasoning with salt and pepper to taste.
Serve the chicken on the biscuit (see recipe). Garnish with scallions.