Preheat oven to 375°F (190°C) and grease a 9×13-inch baking dish
Cook chicken breasts in 2 tbsp olive oil in a skillet over medium heat until no longer pink inside (about 12-15 minutes)
Remove chicken, shred using two forks, and place in a large mixing bowl
Sauté 1 diced onion, 3 minced garlic cloves, and 1 diced bell pepper in the same skillet with remaining oil until softened (5-7 minutes)
Add diced green chiles to the sautéed vegetables and stir
Mix shredded chicken with softened cream cheese, sour cream, and enchilada sauce in the bowl
Layer 4 tortillas in the bottom of the baking dish
Spread half the chicken mixture over tortillas, then sprinkle with half the sautéed vegetables and chiles
Top with 10 corn tortillas to form a second layer and cover with remaining chicken mixture
Spread enchilada sauce over the top and sprinkle with shredded cheddar cheese
Bake for 35-40 minutes until bubbly and golden brown, then let rest 10 minutes before serving