Heat a large skillet over medium heat. Add the olive oil and chopped sweet onion. Sauté for about 4 minutes or until the onion is tender, stirring occasionally.

Add the minced garlic and cook for an additional 30 seconds until fragrant.

Stir in the chopped chipotle peppers, dried oregano, and ground cumin. Let them toast for about 1 minute to release the aromas.

Pour in the fire roasted tomatoes, chicken stock, and salt. Bring the mixture to a simmer and cook for 7 minutes to let the flavors meld.

Carefully transfer the tomato mixture to a blender and blend until completely smooth.

Return the blended sauce to the skillet over low heat.

Fold in the shredded chicken and cook for about 5 minutes until the chicken is heated through and well coated. Taste and add more salt if needed.

Prepare your garnishes while the chicken simmers.

To assemble, lightly warm the corn tortillas. Top each with a generous portion of chicken tinga.

Garnish with avocado slices, fresh cilantro, diced red onion, and crumbled cotija cheese. Serve immediately with fresh lime wedges.