Season chicken on all sides with salt and pepper. Place the chicken in a shallow dish. Combine the buttermilk, green onions, garlic, and green peppers and the buttermilk. Pour the buttermilk mixture over the seasoned chicken, cover, and marinate for 24 hours, in the refrigerator.

Heat the canola oil in a deep pot to 350 degrees F. Be careful not to fill the pot more than halfway so the oil doesn't boil over when the chicken is added. Place the flour in a shallow dish and season with salt and pepper. Remove the chicken from the marinade and dredge in the seasoned flour, shaking off any excess. Fry the chicken until crisp, amber brown in color, and cooked through, about 20 minutes. The dark meat will take a little longer to cook. While the chicken is frying, make your roux.

In a large, deep soup pot over medium heat, add the oil. Stir in the flour and cook, stirring often, until the roux is peanut butter colored, about 10 to 15 minutes. Whisk in the chicken stock and add the onions, bell pepper, and celery. Bring to a simmer and season, to taste, with salt and pepper.

Drain the fried chicken on clean paper towels and add to the thickened chicken stock mixture. Cook for 30 minutes under a low flame. Serve chicken over white rice with a little extra gravy. Garnish with some green chopped onions and enjoy.