Heat the oil in a Dutch oven over medium heat. When hot, whisk in flour. Continue whisking until the roux has cooked to the color of chocolate milk, 10-12 minutes. While roux is cooking, saute onions, pepper, celery and sausage about 5 minutes in hot skillet. Stir onion, bell pepper, celery, and sausage into the roux; cook 5 minutes. Stir in the garlic and cook another 5 minutes. Season with salt, pepper, and Creole seasoning; blend thoroughly. Pour in the chicken broth and add the bay leaves.