Place the chicken breasts, diced onion, minced garlic, enchilada sauce, chicken broth, cumin, chili powder, and oregano into the crockpot. Cover and cook on low for 4-5 hours until the chicken is tender and easily shredded.
Remove the chicken from the crockpot and transfer it to a large bowl. Use two forks to shred the chicken into bite-sized pieces, watching for the hot steam and ensuring the meat is evenly torn apart.
Stir the shredded chicken back into the crockpot with the remaining sauce, mixing well to coat all the meat evenly and absorb the flavorful spices.
Preheat your oven to 375°F (190°C). Warm the tortillas briefly in the microwave or on a skillet to make them flexible and prevent tearing.
Spread a thin layer of the chicken mixture onto each tortilla, then sprinkle with shredded cheese and optional jalapeños or beans for added flavor.
Roll up each filled tortilla tightly and place them seam-side down in a greased baking dish, arranging them close together.
Top the assembled enchiladas with the remaining enchilada sauce and shredded cheese, then place in the oven.
Bake for about 20-25 minutes until the cheese is melted and bubbly, and the edges are lightly golden.
Remove from the oven and let sit for a few minutes to settle. Slice into portions and serve hot, garnished with fresh cilantro or sour cream if desired.