Quick Chicken and Zucchini Quesadillas

Ingredients

• 4 tablespoons unsalted butter, divided
• 1/2 medium onion, thinly sliced
• 2 medium cloves garlic, thinly sliced
• 2 medium zucchini, halved lengthwise, thinly sliced crosswise
• Kosher salt and freshly ground black pepper
• 1 to 2 chipotles, chopped, plus 2 teaspoons adobo sauce from one can
• 2 cups shredded roast chicken meat
• 1/2 pound Mexican melting cheese, such as queso Oaxacan, or Monterrey Jack, grated on a box grater
• 8 corn tortillas
• Guacamole, for serving

Directions

1. Heat the oven to 250 degrees F, and tuck an oven-safe plate inside to warm. In a large cast-iron skillet over medium heat, melt 2 tablespoons butter. Add the onion, garlic, and zucchini, then season with salt and pepper. Let everything cook, giving it a stir now and then, until the onion and zucchini are soft and just beginning to color, about 7 minutes. Mix in the chipotle and adobo sauce, and cook for 1 minute. Add the chicken and keep it moving until it is heated through, about 2 minutes. Taste for salt and pepper, spoon the filling into a large bowl, and set it aside.
2. Give the skillet a quick wipe, then put it back over medium heat. Warm the tortillas 1 at a time in the skillet until they bend easily, about 10 seconds per side, and move each one to a work surface as you go. Add 3 tablespoons of the chicken mixture and a generous handful of cheese to each tortilla, then fold it over the filling.
3. Melt 1 tablespoon of butter in the skillet over medium heat until it bubbles up. Lay in half of the quesadillas in a single layer, turning them so both sides pick up some butter. Cook until the underside is pale golden and crisp, 3 to 4 minutes, then flip and cook the second side for 3 to 4 minutes longer. Move the finished quesadillas to the warm plate in the oven, then cook the remaining quesadillas the same way with the remaining butter. Serve with a generous dollop of guacamole on the side.