You can make a vegetable pot pie with leftover vegetables, but if you want to show off, use fresh vegetables and steam them before sauting them for a few minutes with onion and garlic so theyre even more delicious. The sauce will be delicious if you make it yourself with nice homemade chicken stock instead of using a can of soup. I make the filling a day before so the flavors can mix well and so that my pot pies are delicious.