Heat a large skillet over medium heat with 1 tsp oil. Brown the sausage in the pan. Remove the sausage from the pan and add the onions. Cook for 1 minute and add the celery, apple, garlic, thyme, sage, salt and pepper. Cook until soft. Add the chicken stock. Scrape up any brown bits from the bottom of the pan. Bring to a simmer and remove from the heat. Set aside until cool enough to handle. Remove the thyme stems mix with the cornbread. Place in a baking dish.