Casserole is a word used to refer both to an ovenproof cooking vessel, and to a baked, savoury food item that is baked in it.
The ingredients in a casserole recipe are usually bound with some kind of sauce. Often, the ingredients are leftovers, or quick to assemble items. There will often be toppings such as crumbs, tomato slices or cheese for visual appeal.
Casserole-style recipes are popular because food baking in the oven doesn’t need a lot of constant watching, and if someone is late to dinner, it’s easy to hold the meal a bit longer without it getting ruined.
In America, tuna casserole might be the most popular casserole, followed closely by Green Bean Casserole at Thanksgiving.
One French equivalent dish of an Anglo-Saxon casserole might be a “cassoulet”, such as “Castelnaudary Cassoulet”, which is made in a pottery vessel called a “cassole.”
Casserole cooking hearkens back to slow-cooking dishes in earthenware containers, even though at the turn of the 1900s home economists hailed it as the way forward for busy, efficient housewives.
In the classical French cooking definition “casserole”, it was a dish was made with cooked rice. You’d make a ring or hollowed-mound of cooked rice, and bake that on its own a bit to stiffen it, then put ingredients inside and bake further. This influenced the more general Victorian definition of casserole as a rice dish.
Gradually, particularly because of American influence at the start of the 1900s onwards, casserole came to mean anything cooked in a casserole dish.
Starting with Campbell’s in the 1940s promoting casserole recipes for its creamed soups, Casseroles largely came to be an assembly of pre-made items. In the 1900s, the height of popularity was in the 1950s and 1960s; by the 1970s, cooks who were starting to learn about antipasti and quiche came to look down on the humble casserole.
Literature & Lore
“To dres Rabbits in Casserole. Divide the Rabbits into Quarters, you may lard them or let them alone just as you please, shake some Flour over them, and fry them with Lard or Butter, then put them into an earthen Pipkin with a Quart of good Broth, a Glass of White Wine, a little Pepper, and Salt if wanted, a Bunch of Sweet Herbs, and a Piece of Butter as big as a Walnut rolled in Flour; cover them close and let them stew Half an Hour, then dish them up and our the Sauce over them. Garnish with Seville Orange cut into thin Slices and notched, the Peel that is cut out lay prettily between the Slices.” — The Art of Cookery, Made Plain and Easy, Hannah Glasse. 1747.
Called “hotdish” in Minnesota.