Place chicken in large pot on the stove and boil about 20-30 mins. Cut into chicken to see if it is cooked. (Don't over cook, you can even slightly undercook since the casserole will be cooked later.)
In another pot, add cream of chicken, cream of mushroom and green chili. Add about 2 cups of water or chicken broth. Stir and heat on medium until sauce is warm. Add garlic powder for flavoring. (Add more water if needed. Sauce should be about the consistency of spaghetti sauce or slightly thinner. Feel free to add more cream of chicken or mushroom also if you like lots of sauce).
While cooking your chicken, shred your corn tortillas into small inch like pieces. Save for layering.
Once chicken is cooked, take out of pot and let cool for a few minutes. Then shred chicken.
In a 9X13 pan spread a thin layer of sauce on the bottom of pan. Then put a layer of corn tortilla down making sure to cover the entire area. Next spread half the shredded chicken, followed by a layer of cheese. Finish the layer by covering with sauce. Make sure entire area is covered with sauce. Start again with the corn tortillas, the rest of the chicken, cheese and end with your sauce.
Cover with foil and cook at 350 degrees for about 45-60 minutes until cheese is bubbling.
Let cool for 5- 10 minutes. Enjoy!