A casserole, from the French for "saucepan", is a large, deep dish used both in the oven and as a serving vessel. The word casserole is also used for the food cooked and served in such a vessel, with the cookware itself called a casserole dish or casserole pan. In British English, this type of dish is frequently also called a bake, coinciding with the cooking technique used to cook casseroles.
Ok so maybe this is a casserole because it is cooked in a casserole!
Mashed Potato Casserole
Boil about 500g potatoes until tender. Drain and mash with 30g butter unitl smooth. Spread over the base of a lightly oiled baking dish(casserole).
Beat 2 eggs with 300ml cream. Add 1 cup grated cheese and 2 T fresh chives (I didn't have any this time so I used rosemary). Pour this mixture over potatoes. Bake at 180 degrees for about 40 mins or until top sets and is brown.
(Recipe from Australian Women's Weekly Potatoes)
I served this with pork chops, carrot and parsnip mash and beans...