Place the chicken breasts in the slow cooker, then pour the enchilada sauce over the top, ensuring they are well coated.
Add the chopped onion, minced garlic, cumin, chili powder, and green chilies (if using) into the crockpot. Season with salt and pepper.
Cover and cook on low for about 4 hours, or until the chicken is tender and easily shredded. The kitchen will fill with warm, smoky aromas.
Once cooked, open the lid and use two forks to shred the chicken directly in the sauce, mixing to coat evenly. If desired, stir in shredded cheese now for extra richness.
Continue to cook uncovered for an additional 10-15 minutes to thicken the sauce slightly and allow the flavors to meld, listening for the bubbling and thickening sounds.
Turn off the crockpot and give the shredded chicken a final stir, ensuring it’s juicy, flavorful, and coated in a glossy sauce.
Serve the smoky, spicy shredded chicken as a filling for tacos, burritos, or over rice. Enjoy the tender texture and bold flavors in every bite!