In a small bowl, mix the chipotles with the Cotija cheese and set aside. Then coat the bottom of a large sauté pan with the oil.
Place the pan over medium heat, add 1 tortilla in the center of the pan (or 2 if they fit) and sprinkle it with an even layer of about half of the Mozzarella cheese. Now sprinkle an even layer of about half of the Cotija-chipotle mixture on top.
Once the cheeses have melted, add about half of the cilantro leaves on top, and then place 4 of the mango slices on half of the prepared tortilla (still in the pan).
Squeeze a bit of lime juice over everything, and then use a spatula to fold the side of the tortilla without the mango, directly on top of the other side. Gently press on top to be sure everything is held together.
Once it's nicely browned, remove the quesadilla from the pan, place it on a clean, dry cutting board, and cut it into however many slices you'd like. Repeat the above, if you didn't do both quesadillas at once.