Boil chicken until done, then cube. Chop the tortillas. Mix cream of chicken, mushroom and tomatoes.
Spread half of chopped tortillas on bottom of a casserole dish. Then on top of tortillas spread half of the cubed chicken. Next pour half of the soup mixture on top of chicken. Spread soup mixture evenly across the layer of chicken. Then sprinkle part of the grated cheese over the soup mixture. Then repeat all the steps to make 2 complete layers.
Stick in the oven at 180 degrees C. Cook for 45 minutes to 50 minutes. Pull out of oven and let cool for 10 minutes and serve.