1) Add stock ingredients to a large pot with enough water to cover everything, 8-10 cups. Bring to a simmer and simmer on low, covered, for at least 2 hours.
2) Remove chicken pieces from stock. Remove skin from chicken and shred the pieces into large chunks. Strain the stock.
3) Add stock and chicken back to large pot.
4) To make roux, stir oil and flour together over medium-low heat until it turns a nice dark color. The lightest it should be is the color of peanut butter, but you can go much dark. Stir regularly while it’s cooking so it doesn’t burn. It will take at least 20 minutes to get to the right shade.
5) Dice up onions, bell peppers, and celery for finishing ingredients. Split into two piles.
6) Add one pile of diced veggies to the roux when it’s the shade you want. That will stop the cooking process for the roux. Stir together veggies and roux.
7) Saute the second pile of veggies in a skillet over medium-high heat with a drizzle of olive oil and a pinch of salt. Cook until softened, about 4-5 minutes.
8) Bring stock and chicken to a simmer and start adding roux mixture to it. Add it in large spoonfuls and make sure it dissolves completely before adding more. It’ll take 5-10 minutes to add all the roux to the stock. Continue to simmer for 20 minutes uncovered to thicken the mixture. If you’re using browned sausage (like andouille) add it now.
9) Add sauteed veggies to gumbo and white wine. Season with hot sauce and salt and pepper.
10) Serve gumbo over rice sprinkled with file powder. Garnish with scallion greens.