Butter upon bacon is a Victorian way of saying that's too much. One good thing would have done; you have added another on top.

J. Redding Ware recorded it in 1909 under the label Household English — the language of kitchens and family tables rather than streets or stages — and defined it in a single word: Extravagance.

He also explained where it came from, and the explanation is a small piece of social history. The phrase grew, he said, out of the condemnation of eating bread and butter with bacon, instead of the plain loaf. The logic is easy to follow: bacon was rich enough, and came with its own fat. Spreading butter on the bread beside it was doubling up — a luxury on a luxury — and in a careful household that was the kind of thing you were told off for.

By Ware's time it could be used of anything overdone. Ware's example is about dress, not food: What — are you going to put lace over the feather — isn't that rather butter upon bacon? A feather was already a statement. Lace on top of it was showing off.

That is what makes the phrase useful still. It is not about waste exactly, or about cost. It is about the moment when adding more stops making something better and starts making it ridiculous — a judgement every household makes, about food, clothes or anything else, and one this phrase delivers in three words.