When my dad was growing up, my grandmother had to make sure the kids got their veggies and proteins, but at the same time she needed to use the leftovers from days before… I don’t know exactly when she came up with the recipe but it’s one that has gone from generation to generation. She would call it the “scraps pie”, by using the left over chicken or meat from the day before (never together though). My favorite from the versions, is definitely this one: with tuna. The “fishy” flavor from the tuna is toned down with both the Bechamel Sauce and the spinach.
Give it a try! This soon will become your left over go-to recipe.