Add oil and 1 1/2 Tbsp of the butter to a dutch oven or large heavy bottomed pot. Heat over MED HIGH heat, and add chicken pieces. Season with 1/2 tsp kosher salt, 1/4 tsp black pepper, and 1/2 tsp poultry seasoning.
Cook until golden brown and cooked through, about 5 minutes, stirring often. Remove to a plate.
Add remaining 1 1/2 Tbsp butter to pot and decrease heat to MED. Add onions and celery and cook for 3-5 minutes, until softened. Stir in garlic and cook another minute.
Add flour and stir to coat. Cook 1 minute to get the raw flour taste out, stirring often.
Pour in wine and 1 cup of the chicken broth, using a wooden spoon to scrape any browned bits from the bottom of the pot. Simmer for a minute or so.
Add remaining chicken broth, half and half, potatoes, thyme, rosemary, onion powder, garlic powder, remaining 1/2 tsp kosher salt, 1/4 tsp black pepper, and 1/4 tsp poultry seasoning.
Increase heat and bring soup to a boil, then reduce heat to MED LOW and simmer for 12-15 minutes, until potatoes are tender.
Use a potato masher to mash about half of the potatoes, so soup is thickened and ultra creamy.
Return chicken to the pot, along with heavy cream, frozen peas and carrots, and corn. Stir well to combine and heat for a few minutes, until combined and heated through.
If soup doesn’t thicken enough for your liking, in a small bowl, mix together 2 Tbsp of cornstarch and 3 Tbsp of water until smooth. Stir that into the soup and cook another few minutes, stirring often.
Serve hot, with biscuits or baked puff pastry squares and sprinkled with a dash of black pepper.