Peel sweetpotato and chop into 1-inch cubes. Place in pot and cover with water. Bring to boil over high heat. Cook 13-15 minutes until sweetpotatoes are tender. Drain and let cool 2-3 minutes then puree in food processor or blender.
Bring large pot of water to boil. Add shell pasta. Cook until slightly harder than al dente as it will continue to cook in oven.
Strain pasta, rinse with cold water and set aside.
To make ground turkey: Heat large skillet over medium heat. Add olive oil. When olive oil is fragrant, add ground turkey. Break turkey into small pieces. Mix in onion, garlic powder, salt, ground pepper and powdered mustard; cook 4-5 minutes. Remove from heat.
To make cheese sauce: Heat oven to 375 F and place sweetpotato puree in blender or food processor with tomato puree, chicken broth, 1 cup shredded cheese and salt, to taste. Blend until combined and sauce is smooth.
Spray 9-by-13-inch casserole dish with nonstick cooking spray. Place noodles, ground turkey and sweetpotato sauce in casserole dish and mix until coated in sweetpotato cheese sauce. Sprinkle with additional shredded cheese, if desired, and bake 15 minutes.
Remove, let cool 10 minutes and sprinkle with fresh parsley.