Chicken Thigh and Smoked Sausage Gumbo

Name: Chicken Thigh and Smoked Sausage Gumbo
Ingredients: 8 bone-in skin-on chicken thighs; 3 tablespoons Cajun seasoning; 1 cup corn oil; 1 cup all-purpose flour; 2 cups chopped yellow onion; 1 cup chopped celery; 1 cup chopped green bell pepper; 2 cups chopped okra; 1/4 cup chopped garlic; 1 pound smoked pork sausage, sliced; 2 tablespoons Worcestershire sauce; 1 tablespoon kosher salt; 1 tablespoon ground black pepper; 3 bay leaves; 10 cups chicken stock; 2 cups beef stock; 1 cup chopped green onions; 1 teaspoon cayenne pepper; 2 tablespoons file powder, plus more for garnish