Cassoulet means casserole. It is French, but it is based on using meats with a type of large bean. I think Americans throw whatever they have together and call it a casserole, but at it's heart, a cassoulet is not necessarily about "leftovers".
Here's where I may have gone wrong. I got my recipe made from leftovers from the cook at a French countryside B&B. I thought she said it was a traditional French peasant
dish. She may have meant that it was a traditional French
recipe for a cassoulet.
As I was discussing this with Marcia she found this passage on Wikipedia (hardly an expert source), "Haute cuisine versions require mixing pre-cooked roasted meats with beans that have been simmered separately with aromatic vegetables, but this runs counter to cassoulet's peasant origins." The precooked (leftover) aspect that I have clung to for several years may not be correct at all.
I wonder if there was an old lady in France chuckling until her last days over the story she told "that American."