Spray a 6 quart crock pot with a non stick spray.
Add onions, garlic, chicken breasts, *roasted Hatch chiles to crock pot and pour a 15 oz can of green enchilada sauce over chicken, sprinkle with cumin and pepper.
Cover and cook on high for 5-6 hours. Once done, shred chicken and leave in crock pot until ready to assemble the enchiladas, then scoop out shredded chicken with a slotted spoon to remove the excess liquid when adding to baking dish.
Spray a large baking dish with a non stick spray and pour about a cup of enchilada sauce into the bottom (I used a 14 x 11 1/2 x 2 1/4 baking dish).
In a medium saucepan, pour the 28 oz can of green enchilada sauce into the pan. Turn on medium and once heated, dip each corn tortilla into the sauce.
Add a layer of tortillas to the bottom of dish which will overlay on each other.
Spoon about 4 -5 heaping tablespoons of sour cream onto the tortillas and spread out covering as much of the tortillas as possible.
Add a layer of shredded chicken, cheese, olives and then repeat the layering again ending with a layer of tortillas, cheese and black olives.
Cover with foil and bake for 60 minutes, remove foil and place back in the oven for an additional 15 minutes.
Remove from oven and serve with beans and rice.
*How to roast chiles: Place chiles on a foil lined baking sheet. Place in 500° oven on the top shelf and roast for about 7-8 minutes on each side. Carefully remove from baking sheet and place in a large baggie. Seal and let steam for about 10 minutes. Remove one at a time and peel the skin from each chile. Cut off stem and remove seeds. Chop, add to crock pot on top of chicken.