Place chicken breasts, taco seasoning, and red enchilada sauce in the slow cooker. Cover and cook on LOW heat for 4 hours or until the chicken is cooked.: As the ingredients start to warm, you will notice the sauce loosening and the spices perfuming the air with warm chili and cumin notes. The surface of the sauce should shimmer slightly as steam begins to rise, and tiny bubbles may form at the edges after a short time on low. This stage builds flavor because the spices bloom in the hot liquid and begin penetrating the chicken , so even distribution matters. If the seasoning seems clumpy, stir gently to coat the meat evenly. A typical pitfall is adding too little liquid, which can cause uneven cooking or overly concentrated taste, so ensure the sauce sufficiently covers the meat's bottom area.
Remove the chicken from the crockpot and shred it with two forks. Return the chicken to the slow cooker. Add shredded cheddar cheese and chopped corn tortillas and stir.: During these hours the aroma will deepen, becoming richer and slightly smoky from the taco seasoning. You will see the sauce reduce slightly and the chicken fibers relax, meaning the meat becomes tender and ready to shred. The slow, consistent heat allows collagen to break down, keeping the meat moist and shreddable, which is why low and slow is preferred over quick high heat. Avoid frequent lid lifting, as heat loss prolongs cooking and can dry the surface. If the cooker runs hot and the sauce reduces too quickly, add a splash of water, but avoid diluting the flavor too much.
Cover and cook on HIGH heat for 30 to 45 minutes, until the tortillas are tender and the cheese has melted. Garnish with black olives, tomatoes, and fresh cilantro.: When you lift a fork through the meat it should part with little resistance and reveal delicate strands. The sound is subtle, a soft tearing rather than a wet squelch. Shredding increases the surface area so the sauce clings to more of the meat, enhancing every bite. Use two forks to pull across the grain for thin, even shreds. A common misstep is shredding while the meat is too hot to handle, so let it rest briefly until comfortable to touch, or use tongs to stabilize pieces while shredding.
Return the chicken to the slow cooker: Once shredded and folded back into the sauce, the chicken will soak up more flavor and the pieces will glisten as they absorb the liquid. Stir gently to keep strands intact while ensuring even distribution. This step encourages the meat to marry with the sauce so each spoonful is saucy and seasoned. Over stirring can cause the texture to break down into mush, so be deliberate and gentle. If the mixture looks too dry after stirring, add a few tablespoons of reserved sauce or warm water to reach the desired consistency.
Add shredded cheddar cheese and chopped corn tortillas and stir: As you fold in the shredded cheddar cheese and cut corn tortillas , you will see the cheese begin to tack to the warm sauce and the tortilla strips start to soften at contact. The tortillas will soak up liquid and swell slightly, which creates the layered, soft texture we want. Work quickly so the cheese begins to meld but does not clump, and ensure tortillas are evenly distributed to avoid dry pockets. If you notice clumping of cheese, stir in small circular motions and break apart any lumps with a spoon.
Cover and cook on HIGH heat for 30 to 45 minutes, until the tortillas are tender and the cheese has melted: On high the casserole will bubble more vigorously, and you should hear gentle pop and fizz at the edges where sauce meets cooker wall. The aroma will intensify with melted cheese notes rising alongside warm chili spices. Watch for the tortillas to become uniformly soft rather than gummy, and aim for a gentle bubbling that indicates heat penetration without scorching. A key sign it is ready is when the cheese is fully melted and the casserole jiggles slightly in the center when nudged. Avoid leaving it on high much longer than suggested, as the tortillas can disintegrate and the texture may become pasty.
Garnish with black olives, tomatoes, and fresh cilantro: Fresh garnishes bring brightness and contrast to the rich casserole. The tomatoes add a juicy pop, the cilantro a citrusy herb lift, and the olives a briny counterpoint. Sprinkle them just before serving to preserve color and texture. Over garnishing too early can lead to wilted herbs and waterlogged toppings, so add them at the table for the best presentation.