Chop mushrooms, celery, carrot, onion, and garlic. Sauté in the olive oil.
Add ground turkey to vegetables. Sprinkle the turkey with salt, pepper and any other spices you would like to include.
Remove the stems of the banana peppers. Slice peppers down the middle to split open and remove any seeds.
Pour enough of the juice from the canned tomatoes in a glass 9 by 13 pan to cover the bottom. Line the peppers in the pan.
Roast peppers in the oven until tender/easily pierced with a knife. Mine took about 15 minutes.
Once mixture is cooked through, and peppers are roasted, spoon turkey & veggies into banana peppers.
Once all peppers are filled, pour canned tomatoes and remaining juice over peppers.
Place back in the oven to heat tomatoes and peppers through - about 15/20 minutes.
Place in a high powered blender tomatillos, onion, garlic, cilantro, oregano, cumin, salt and water. Blend until completely smooth and it has a salsa consistency. I only had a red onion left when I made mine, so I used that! Use whatever you have on hand. Because I also received a green tomato in my weekly CSA I threw that in the blender as well.
If you'd like to add cheese, sprinkle cheese on peppers and leave in oven until melted.
Take out of the oven and let sit for a few minutes. Plate pepper onto dish and drizzle tomatillo salsa on top. Enjoy!