Preheat your oven to 375 F. Place chicken breast, skin side up, on a baking sheet; drizzle with one tablespoon of oil and season with salt and pepper. Roast for 45 minutes, until chicken juices run clear. Remove from oven and let cool while you prep the rest of the filling.

Heat a large skillet to medium-high and add remaining tablespoon of oil. Sauté onions until they soften and begin to brown on the edges, about 5-6 minutes. Add garlic and cook for one more minute. Add chopped olives and one cup of enchilada sauce; cook for one more minute.
Remove onion mixture form heat.

Once the chicken is cool enough to handle, remove skin and pull the meat off the bone. Shred with a fork and stir into onion mixture.

Spray a 9" x 13" glass baking dish with nonstick cooking spray. To assemble the enchiladas, place one tortilla on a work surface and add about 1/3 cup of the chicken mixture and a handful of cheese. Roll the tortilla up and place in your baking dish. Continue this process until all tortillas are gone. Pour remaining enchilada sauce of assembled enchiladas and sprinkle remaining cheese over sauce. Bake at 375 F for about 30 minutes, until the enchiladas are heated through and cheese is bubbling. Remove from oven and let stand to cool for about 5 minutes. Garnish with green onions and serve immediately.