Cook the chicken breast in hot water, with a little salt and pepper, for about 20 minutes. Take the chicken breast out of the cooking water and let it cool. Once it's cool enough to handle, use your fingers to shred the chicken into thin, 1-inch long pieces.
While the chicken is cooking, cut the tortillas into strips or triangles.
Fry the cut tortillas in oil. Use only the necessary oil so that they brown and become crisp.
Remove the tortillas from the oil and place them on a plate covered with absorbent paper, to remove excess fat.
Once the chicken is cooked, shred the meat with the help of two forks. Reserve.
Heat the sauce in a saucepan. Normally, the chilaquiles sauce does not have a thick texture, so it can be diluted with a little water, taking care of the quantity so as not to lose the seasoning. Correct with a little salt and pepper, if necessary.
While the sauce is heating, peel and chop the onion into very thin wheels and then separate the inner circles. Reserve.
Before removing the sauce from the heat, add the chicken and the fried tortilla pieces. The idea is that the pieces are soaked in the sauce, but without leaving them long enough to lose their crunchy texture. Mix quickly.
Serve immediately with the help of a ladle, placing a portion of salsa with tortillas on each plate.
Decorate the portion of each plate with a little cream of milk.
Sprinkle chopped cilantro and grated or crumbled cheese over each plate.
Finish the decoration with thin onion wheels, on top of the other ingredients.