Wash and dry sweet potatoes and pierce them all over with a fork. Bake sweet potatoes 50 to 55 minutes, until soft.
Heat a large deep nonstick skillet over high heat and brown the ground turkey, seasoning with 1 teaspoon salt and cook, breaking the meat up with a wooden spoon as it cooks about 5 to 6 minutes.
Reduce heat to medium low, push the meat to the side and add the oil, onion, celery garlic, and tomato paste. Cook until the vegetables are tender, about 5 minutes then mix.
Add the frozen vegetables, mushrooms, Worcestershire sauce, fresh thyme and mix well.
Whisk together the broth and flour in a small bowl and pour over meat. Simmer, covered on low about 5 minutes, until it thickens and the flavors meld.
When the potatoes are ready, cut them open and top each with a scant cup of the turkey mixture. Eat hot.