Add the water, chicken bouillon concentrate, whole tomato, peeled whole garlic cloves, oregano and chipotle chillies. Once the broth has come to a simmer, blend it in a blender or by using an immersion blender.
Add the shredded chicken to the pot, while still over medium heat. Let the chicken heat through with the broth, and allow some of the broth to evaporate into the chicken.
Heat a cast iron skillet over medium heat. Add some butter, and add the quesadilla to the pan. Cook until brown on both sides, and the cheese has melted.