I had left over pot roast (made with a chuck roast), baby carrots and potatoes. I wanted to do something with it other than a sandwhich... so this Shepard's Pie was my fix. I also didn't have enough gravy for the filling so I sub'd a can of cream of celery. We aren't big peas fans so we went with iron rich Spinach instead. You don't have to do much seasoning and the whole dish is ready in about 30 minutes!