01 - Whisk together olive oil, lime juice, minced garlic, cumin, smoked paprika, chili powder, dried oregano, salt, and black pepper in a medium bowl until thoroughly combined.
02 - Add chicken thighs to the marinade, tossing well to coat completely. Let sit for at least 15 minutes, or up to 2 hours for deeper flavor penetration.
03 - Heat a large skillet or grill pan over medium-high heat. Cook marinated chicken thighs for 5–6 minutes per side until cooked through and nicely browned with a slight char.
04 - Transfer cooked chicken to a cutting board and let rest for 3 minutes to allow juices to redistribute. Chop into bite-sized pieces.
05 - Heat corn tortillas in a dry skillet or directly over a gas flame for about 30 seconds per side until soft, warm, and pliable.
06 - Fill each warmed tortilla with chopped chicken. Top generously with diced white onion, fresh cilantro, avocado slices, and cotija cheese if desired.
07 - Serve immediately with fresh lime wedges and salsa or hot sauce on the side for squeezing and drizzling.