Boil a large pot of salted water and cook pasta. Remove pasta from heat just a little bit before it’s done to your liking and drain. Set aside in the colander.
Meanwhile, heat the pot roast in a large skillet. You can either warm it with its sauce, or you can crisp it up a bit and add a little sauce later.
In the pasta pot, heat evaporated milk over medium low. Add cheese a handful at a time until it’s all melted. Stir for 30 seconds or so until a smooth sauce forms. Remove from heat.
Stir pasta into cheese sauce; sauce will continue to thicken slightly. Serve immediately, topped with warm pot roast, kettle chip crumble, and chives!