Season the chicken. Place the chicken in the slow cooker. Sprinkle on taco seasoning, cumin, and smoked paprika.
Pour in the salsa, diced tomatoes with green chiles, and chicken broth.
Cook low and slow. Cover and cook on Low for 4–6 hours or on High for 2–3 hours, until the chicken is tender and shreds easily with two forks.
Shred the chicken. Transfer the chicken to a cutting board and shred. Stir it back into the slow cooker juices. If using corn or black beans, fold them in now.
Make the queso. In a small saucepan over low heat, whisk the evaporated milk with cornstarch until smooth.
Add the cheese and stir frequently until fully melted and creamy. If it seems too thick, add a splash more milk; too thin, let it gently simmer a minute.
Combine. Pour the warm queso into the slow cooker and stir until the chicken is evenly coated and saucy. Taste and adjust seasoning with salt, pepper, or more hot sauce.
Warm the tortillas. Wrap tortillas in foil and warm in a low oven, or heat them in a dry skillet until soft and pliable.
Warm tortillas make the tacos taste better and hold together.
Assemble and serve. Spoon the queso chicken into tortillas. Top with fresh garnishes like cilantro, lime, and jalapeños. Serve immediately while everything is hot and melty.