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, toss to coat evenly, and let sit at room temperature for at least 15 minutes or refrigerate for up to 2 hours for deeper flavor penetration.
03 - Heat a large skillet or grill pan over medium-high heat. Cook chicken thighs for 5 to 6 minutes per side until fully cooked through with an internal temperature of 165°F and nicely browned exterior.
04 - Transfer cooked chicken to a cutting board and let rest for 3 minutes to retain juices, then chop into bite-sized pieces.
05 - Heat corn tortillas in a dry skillet or directly over a gas flame for approximately 30 seconds per side until soft, warm, and pliable.
06 - Fill each warm tortilla with chopped chicken, then top with diced white onion, fresh cilantro, avocado slices, and crumbled cotija cheese if desired.
07 - Serve immediately with fresh lime wedges and salsa or hot sauce on the side for squeezing and drizzling.