1. Wrap the chicken in paper towels to dry. In a large cast iron Dutch oven over medium high high, melt 1 tbsp of the oil until just smoking. Add as much chicken as fills one layer at the bottom, and cook until browned, about 5-7 minutes per side. Continue to cook the chicken in batches as needed, adding oil if needed. Set aside all seared chicken on a separate plate.
Chop half of the pine nuts (ideally in a food processor, but if you don't have one, I usually put them in a plastic bag and beat it with a meat tenderizer, just be careful not to rip the bag!). Heat 2 more tbsp of oil in the Dutch oven. Add the onion and cook while stirring for about 5 minutes until softened.
Add the garlic, chopped pine nuts, 3 tbsp of ground sumac and paprika. Cook for about 30-60 seconds, then add the water and bring to a simmer. Return the chicken to the pot, cover, and reduce the heat to medium low. Cook until tender, about 26 minutes.
Heat the oven to 450 degrees F with a rack in the center position. Use a slotted spoon to take out the chicken, place it in a bowl, and shred the meat with two forks. Bring the liquid to a simmer over medium high, and stir until most of the moisture has evaporated, about 10 to 15 minutes.
Return the chicken to the pot and stir in the remaining 1/4 cup of pine nuts. Taste and season with salt and pepper. Cover and set aside.
Brush the pita with olive oil and arrange on a rimmed baking sheet. Bake for about 5-7 minutes until browned on the edges. Sprinkle both sides of the pita with ground sumac. Stir the parsley into the chicken. Serve on top of warm pitas with tahini drizzled on top.