In a medium skillet, heat the tablespoon of oil over medium-high heat. Add the sliced sausage and cook for 5 minutes or until most of the fat has rendered. Remove the sausage to a paper towel lined plate to drain; set aside.
In a large dutch oven, heat the remaining oil over medium-high heat. Using a whisk, gradually stir in the flour. Whisk until combined. Lower the heat to medium-low and continue whisking until the roux is a dark nutty brown color, about 20-30 minutes. (Be careful not to burn the roux.)
Immediately add the onion, celery and bell pepper. Stir to combine with the roux. Add the garlic. Cook for another 10-15 minutes, stirring frequently. Add the thyme and bay leaf. Stir in the stock, reserved sausage and turkey. Bring to a boil. Reduce the heat to low and simmer for 2-3 hours. Skim any fat that surfaces and discard.
In a small bowl, whisk together the cornstarch and additional stock/water until cornstarch has dissolved. Bring the gumbo to a rolling boil and add the cornstarch mixture. Stir the gumbo until it begins to thicken. Reduce the heat to medium and cook for another 5 minutes. Season to taste with salt, pepper, and cayenne, if using. Remove from the heat and allow to rest while you prepare the rice. Serve in bowls over the rice. Garnish with chopped green onion and a few dashes of Tabasco if using. Enjoy!