Place a chicken breast into a large Ziploc bag, close the bag almost all the way, then pound the chicken to a thickness to 1/2-inch thick; repeat with remaining breasts and set aside.
Combine the grated cheese, cream cheese, onion, garlic, cilantro (if using), 1/4 teaspoon of ground cumin, and 1 teaspoon of chili powder in a bowl and stir well.
Take each canned whole chile pepper and stuff with a quarter of the cheese mixture.
Take a flattened chicken breast and place a cheese-stuffed chile pepper on top, then roll the chicken breast around the pepper and fold in the sides; secure the roll with wooden toothpicks so that the toothpicks are as flat against the meat as possible (makes dredging easier).
Repeat with all breasts and chile peppers.
Beat the egg and milk together and pour into a shallow dish or pan.
Combine the bread crumbs, garlic powder, the remaining cumin and chili powder, and salt, and pour onto another shallow dish or pan.
Dredge the rolled chicken breast in the egg mixture, then in the bread crumbs and coat well.
Bake the rolls on an un-greased baking dish, uncovered, at 375 degrees F for about 40 minutes and the meat is tender and juices run clear.
Remove and discard toothpicks.
Garnish with chopped green onions and serve with a bit of sour cream/guacamole and Mexican rice.