Boil your chicken breast in some water and chicken base for about 20-30 minutes. Don't overcook your chicken because it will cook more in the oven.
Turn off heat. Remove chicken from broth and cube/dice. Set aside.
While chicken is cooking, chop up onion and bell pepper. Saute' in skillet with 1/2 stick of butter til el dente'. (Will cook more in oven.) Turn off heat when done.
Dip 6 corn tortillas into chicken broth and layer in a large casserole dish, lining the bottom and sides of dish. Layer 1/2 diced chicken, 1/2 bell pepper and onion mixture, 1/2 can cream of mushroom soup, 1/2 can cream of chicken soup, 1/2 T. chili powder, and 2 T. picante sauce (I use medium).
Dip remaining (6) tortillas in chicken broth and layer on top. Repeat layering with diced chicken, soups, onion & bell pepper, chili powder and picante sauce.
Finish your casserole by adding a can of diced or stewed tomatoes to the top and 1 cup of shredded cheese. If you would like your casserole to be spicier, use Rotel instead of plain tomatoes on this step.