Layer the slow cooker. Add chopped onion, garlic, corn, and diced tomatoes to the bottom of the slow cooker. Sprinkle smoked paprika, cumin, chili powder, salt, and pepper over everything.
Add the chicken. Nestle the chicken breasts or thighs on top of the corn mix. Pour the chicken broth around the edges (not directly on top — keep some flavor integrity). Dot with butter if using.
Cook low and slow. Cover and cook on low for 4–5 hours or on high for 2–3 hours. You want the chicken tender enough to shred easily. Resist peeking too often — the slow cooker judges you.
Shred the chicken. Remove the chicken to a bowl and shred with two forks. Toss the shredded chicken back into the slow cooker and stir to combine with the corn and juices.
Cream it up. Stir in mayo, sour cream, cotija (reserve some for topping), and lime juice. Taste and adjust seasoning—add more salt, lime, or chili powder to your mood.
Finish and serve. Let it cook uncovered for 10–15 minutes to thicken slightly. Serve over rice, in tortillas, or on toasted buns. Garnish with cilantro, extra cotija, and lime wedges. Eat immediately or risk tragic sogginess.