Pat the thighs dry. Season with 1 teaspoon kosher salt and half teaspoon black pepper. Heat a Dutch oven over medium-high. Add the butter and the oil. Sear thighs skin-side down for 4 to 5 minutes until golden. Flip and sear 2 more minutes. Remove and set aside.

In the same pot, add onion, carrots, and celery. Cook 4 to 5 minutes until softened. Add garlic and cook 1 minute until fragrant.

Pour in 5 and a half cups chicken broth, scraping up any browned bits. Add poultry seasoning and remaining salt and pepper. Nestle the chicken thighs back in. Bring to a boil, then reduce to a simmer. Cover and cook 25 to 30 minutes until chicken is cooked through and tender.

Remove thighs, shred the meat off the bone, and return it to the pot. Discard skin and bones.

In a bowl, whisk together flour, baking powder, and salt. Stir in milk and melted butter until just combined. Do not overmix. Fold in parsley if using.

Drop heaping tablespoon-sized balls of dough onto the surface of the simmering stew. Space them so they are not touching. Cover immediately.

Simmer on low, covered, for 14 to 16 minutes without lifting the lid. Dumplings are done when they are fluffy and cooked through.

Stir in 1 cup of milk to make the broth creamy. Add peas if using. Taste and adjust seasoning.

Let sit 5 minutes off heat before serving. Garnish with fresh parsley and cracked pepper.