When she was more broke than usual my mother used to say she was ‘going on frugals’. Which usually meant a few more than usual of what she called ‘dustbin’ soups, i.e. made with whatever she had - always tasty and filling.
The tradition continues in our house - we don’t even need to be ‘on frugals’ but they’re certainly a good way of keeping food costs down - using up leftovers, plus all sorts of veg, including any looking a bit sad or limp, plus red lentils or pearl barley, or both. A little orzo pasta is another good one.
Favourite leftovers to add in this house are mashed potato (if there ever is any), any leftover cheese or parsley sauce (not often) or any proper gravy left over from a roast.
Plus of course that last, lonely, dried up bit of ham or bacon, snipped up and fried gently with the onion.
Come the autum (season of mists and mellow soupfulness ?) there will be plenty of ‘dustbin’ soups here, using lots of relatively cheap, seasonal, U.K. grown veg.