Combine the avocado, jalapeño, water, cilantro, white vinegar, and salt in your food processor. Blend everything together until the mixture is completely smooth and has a velvety texture. Place the salsa in an airtight container and refrigerate it until you are ready to serve.
Preheat your oven to 400°F (200°C) and lightly grease a baking dish. In a large bowl, toss the chicken thighs with olive oil and all the seasonings until they are well-coated. Add the poblano peppers, onion, garlic, and cilantro, mixing until everything is evenly combined before spreading it in the baking dish.
Bake the chicken mixture for 20-22 minutes, or until the chicken is cooked through and reaches an internal temperature of 165°F (74°C). Once cooked, use two forks to shred the chicken directly in the baking dish. Mix the shredded chicken with the roasted vegetables to soak up all the delicious juices.
Increase the oven temperature to 425°F (220°C) and line a baking sheet with parchment paper. Arrange the corn tortillas on the pan in a single layer and lightly spray them with cooking oil. Bake for 2-3 minutes, just until they are warm and flexible enough to fold without cracking.
Remove the warm tortillas from the oven. On one half of each tortilla, sprinkle a layer of shredded cheese, top it with the chicken and poblano mixture, and then add another sprinkle of cheese. Fold the empty half of the tortilla over the filling and press down gently to seal the taco.
Return the assembled tacos to the oven and bake for 15-17 minutes. You'll know they are done when the tortillas are golden brown and crispy, and the cheese is fully melted and bubbly. Serve them immediately while they are hot and at their crunchiest.