Add the olive oil to a large skillet set over medium heat. Once hot, stir in the diced onion. Cook until the onion's tender, roughly 2-3 minutes.
Stir in the pork, corn, and barbecue sauce, mixing to evenly combine. Allow the mixture to cook until heated through. Remove from heat, and set aside.
In another skillet heating over medium heat, add the butter.
Once melted, add the flour and whisk in until combined. Cook for another 30-60 seconds, just to cook off any flour-y taste.
Slowly pour in the broth, whisking constantly until it's all incorporated and the roux is smooth. Bring the mixture to a simmer, and allow it to cook, whisking often, just until slightly thickened.
Remove the skillet from heat, add the cheese, and continue stirring until the cheese has completely melted and become incorporated with the sauce.
Whisk in the sour cream until the sauce is smooth. Cover the skillet with a lid to keep the sauce hot & smooth.
Begin assembling the enchiladas. Lay a single tortilla out on a flat work surface. Spread some of the barbecue chicken down the center of the tortilla, then roll it up, and place it seam side down in a greased 9x13" baking dish.
Repeat until all the filling's been used and the dish has been filled with stuffed tortillas.
Pour the cheese sauce evenly out over top of the prepared tortillas.
Bake them at 350° for 30-35 minutes.
Serve the cheesy enchiladas with your favorite toppings.