Preheat the oven to 350 degrees. Cook the pasta in a large pot of well-salted water according to package directions until just barely al dente. Drain and set aside.
If you are making pulled pork fresh, follow the directions on your favorite pulled pork recipe and reserve two cups of pulled pork to use here. If you are using leftover, set aside two cups of pulled pork.
Melt butter in a large 8-quart saucepan over medium heat. Add onion, reduce heat to low and cook, stirring frequently until translucent and soft. Whisk in flour and cook for 30 seconds. Whisk in milk slowly. Raise heat to medium high and whisk constantly until the mixture begins to thicken and bubble.
Whisk in your favorite barbecue sauce (homemade or store bought) and ½ teaspoon each salt and pepper. Bring mixture to a low simmer, whisking constantly.
Reduce the heat to low and use a wooden spoon to stir in all cheeses except the remaining ½ cup of Monterey Jack cheese until melted. Stir in the reserved pulled pork and pasta until well coated. Pour the mixture into an oven safe skillet or baking dish.
In a small bowl, mix the panko, Pepper Jack, and olive oil. Sprinkle evenly over the mixture in the skillet.
Bake until the topping is browned and the cheese sauce is bubbling through the topping and around the edges of the skillet, around 40-45 minutes. If the topping begins to brown too deeply, tent loosely with foil. Let the dish rest for at least 15 minutes. Sprinkle with chives and serve.
Recipe by In Good Taste at http://ingoodtaste.kitchen/barbecue-pulled-pork-macaroni-and-cheese/