Put in a pan the guajillo sauce and the water, mix, add some salt and let it boil for about 3 minutes. If you are using other kind of sauce it might not need the water. To make the tortilla chips put the tortillas over a plate in the microwave for 2 minutes, flip the tortillas and leave them again in the microwave for another two minutes. Break the tortillas in pieces and put them on top of the boiling sauce. Add some chicken on top as well as the yogurt and cheese, cover for another 3 minutes and that is it!