Slice the tops off your peppers and remove the cores. Reserve the tops.
Place your peppers in a baking dish (preferably one with a lid - but don't panic if you don't have one). Make sure the dish is small enough to fit the peppers snugly so that they can stand upright.
Pour 2 of the 3 cans of tomato sauce into the bottom of the pot so your peppers have a nice little pool to swim in during baking.
Pop out the middles of your pepper tops and chop them, as well as the onion and mushrooms.
Put your veggies in a pan with the olive oil and sauté until they are nice and soft.
Put your cooked veggies into a large mixing bowl and set aside.
Using the same pan you cooked your veggies in, cook your turkey in the 1/2 cup of broth.
Add your spices.
In the last 3-5 minutes of cooking, return your veggies to the pan. Mix well.
Return the entire mixture to the mixing bowl. Add your remaining tomato sauce. Stir well.
Fill your peppers with the meat mixture.
Cover with a lid. If you don't have one, cover tightly with aluminum foil.
Bake for approximately one hour, or until the peppers are very soft.
Cool and serve with a little sauce poured over the top.
Notes
Please note that the nutrition data below is a ballpark figure. Exact data is not possible.