To make these Baked Chicken Tinga Tacos, start by preparing the cilantro avocado crema. Add the avocados, Greek yogurt, cilantro, jalapeño, garlic, lime juice, and salt to a blender. Blend until completely smooth and creamy. Taste and adjust the seasoning as needed. If the crema is too thick, add a tablespoon or two of water until it reaches your desired consistency. Set aside.
Next, finely shred the rotisserie chicken using two forks and set it aside. Heat a large skillet over medium heat and add the avocado oil. Once the oil is hot, add the diced onion and sauté for about 2 minutes, until it begins to soften. Stir in the minced garlic, fire-roasted diced tomatoes, chopped chipotle pepper, chipotle sauce, chicken broth, cumin, oregano, salt, and black pepper. Let the mixture simmer for 7–8 minutes.
Carefully transfer the sauce mixture to a blender and blend until smooth. Pour the blended sauce back into the skillet and add the shredded chicken. Stir well to fully coat the chicken in the smoky tinga sauce, then remove the pan from the heat.
Preheat your oven to 400°F and line a large baking sheet with parchment paper. Warm the corn tortillas so they are pliable by wrapping them in a damp paper towel and microwaving for about 30 seconds.
To assemble the tacos, spoon a heaping portion of the chicken tinga mixture onto one half of each tortilla and top with 2–3 tablespoons of shredded Mexican cheese. Fold the tortillas in half and place them on the prepared baking sheet. If the tortillas do not stay closed, place a spoon on top while you continue assembling the remaining tacos.
Once all the tacos are assembled, place a second baking sheet directly on top to gently press them down. Bake for 15 minutes, then carefully remove the top baking sheet and continue baking for another 5–7 minutes, until the cheese is melted and the tortillas are golden and crisp.
Remove from the oven and serve topped with the cilantro avocado crema, pickled onions if using, and a sprinkle of crumbled cotija cheese. Enjoy!