How did it happen that we're prepared to pay good money, in restaurants and supermarkets, for modern, luxury versions of what any Victorian housewife would consider "made-dishes": that dainty catch-all name for recipes that recycled leftovers in the days when refrigeration wasn't an option? Kedgeree, fishcakes, bread-and-butter pudding, macaroni cheese, cottage pie: made-dishes all, and on a supermarket shelf near you. And while you're about it, spot these restaurant recyclings on the menu: leftover mussels in the pasta marinara, yesterday's shrimp in the seafood salad, the shreds of someone else's Peking duck in the egg fried rice, tandoori-roasted chicken in the chicken tikka masala.

Waste not, want not, as granny knew well. Scraps from the Sunday beef, leftover slivers of fish, the carcass of a chicken, the last helping of pasta, end-bits from the bread bin, parings from the cheeseboard--it's all good stuff when you know how to use it, which the likes of Isabella Beeton did. And although not everything you'll find in Mrs Beeton's cookery books has made it through to modern times--when was the last time you saw a rissole?--many of these Victorian leftover recipes survived because they taste good. The British love plain food (blame the Anglo-Saxons, who believed that if the meat was good all you had to do was turn it on a spit then slap it on a slab of manchet-bread); but they also love anything in white sauce finished with cheese, baked in a pie or topped with mashed potato. All we ask, it seems, is that we don't have to cook it ourselves.

Turning leftovers into something delicious takes time and a modicum of skill, but that's not the only reason we're prepared to pay someone else to cook them for us. Times have changed. The Sunday roast comes ready-boned, meaning leftovers are in short supply. Few of us want to fillet our own fish for the sake of the scraps, or even trim our own vegetables for the benefit of the stockpot. And if we find there are still tops on the beetroot or greens on the turnips, how many of us would know to shred them, scald them and toss them in garlic and oil with a squeeze of lemon?       

Assuming we do have leftovers left over, though, how do we make the unpromising taste delicious? It's all about adding flavour, whether with ingredients, or in the cooking. Take mince--the ground-up inconvenient bits of animals that the butcher can't sell in any other form. Bulked out with plant-based foods--pasta, potatoes, rice, breadcrumbs--it is the traditional perk of the urban poor. But it is fatty, so it has to be fried gently in a dry pan until the fat runs off and the meat begins to brown. Then you discard the oily residue and add flavour with diced vegetables--onion, carrot, mushrooms, capsicum, celery. Browning the dry ingredients before you add any liquid allows the surface sugars on the meat and vegetables to caramelise. The mouth loves fat and the tastebuds love sweetness.

Caramelising meat and vegetables in leftover dishes also develops umami. The so-called "fifth taste"--the other four being sweet, salty, sour and bitter--was first identified a hundred years ago by a Japanese scientist working in France, and is the secret weapon of the frugal cook. Our flavour-receptors (in the back of the nose, and halfway down the throat) adore it and we will eat pretty much anything in which it's present. Glutamate, the amino acid responsible for umami as a taste sensation, is the raw material of the food additive monosodium glutamate, but it occurs naturally in all sorts of foodstuffs we already recognise as taste-enhancers: cheese, ham, tomatoes and truffles, particularly the Piedmont white.

Umami is most clearly discernible in dashi, the seaweed and bonito-flake broth that forms the basis of Japan's noodle and dumpling dishes, and is available in a dried form that, mixed with water, makes a good alternative to stock. But umami is also prevalent in tomato sauce, soy and Worcestershire sauces, and Marmite--all instant flavour-adders for modern versions of old leftover recipes. Just add some of the above to the mince mixture next time you make cottage or shepherd's pie, and taste the difference. (Incidentally, while monosodium glutamate has a bad name for causing allergic reactions, mostly in Westerners, the Food and Drug Administration in America says it's perfectly safe even for babies, which accounts for its continued presence in many processed foods--including supermarket lasagnes and stir-fries. Dr Kumiko Ninomiya of the Umami Institute of Japan has said that breast-fed babies get their first umami-whack in mother's milk: the glutamate count in human breast milk is ten times higher than in cow's milk. So if you spent all your money on the black diamonds of Perigord or the white pearls of Piedmont, blame your mother.)

Leftovers themselves can add flavour to a dish. Sprouted garlic and onion greens can be chopped and used as a finishing sprinkle on soups and salads. A strip of parmesan rind--or any old scraps of hard cheese--slipped into a tomato sauce will melt in and add flavour along with the protein. Over-the-hill runny cheeses and blues can be pounded up with softened butter or cream and a dash of brandy and potted up for later (French fromagiers sell this at a premium). Leek-tops, celery-root and outside stalks, parsley stalks and dried-out carrots or their peelings will make a stock with a carved-out chicken carcass; add peppercorns for flavour, onion skins for colour and dried-out carrots for sweetness, boil for an hour, strain and boil again till it's lost at least half its volume, pour into ice-cube trays and freeze. You can cook a stock right down until it's sticky enough to dry in the form of little discs--the first soup cubes, as 19th-century travellers took them to sustain them on long sea voyages.

And then there's white sauce, aka béchamel, the point in kitchen history where the plain-cooking English got into bed with the fancy ways of the French. This more than anything else is the unifying agent in expensive, ready-made fish pies, chicken pies, moussakas, and all the imaginative assemblages of vegetables and pasta in the supermarket cook-chill cabinet. It adds smoothness, richness, protein and fat to a dish--and it's so simple. To prepare 500ml of coating-sauce--the consistency required for all leftover dishes--take a smallish, heavy-bottomed pan and fry a heaped tablespoon of flour in a level tablespoonful of butter or oil, stir for a minute or two over a gentle heat until it turns sand-coloured--stop before it browns, though, or it will taste bitter-then gradually whisk in 500ml hot milk, stock, or a mixture of both. Carry on stirring till the sauce is smooth and thick enough to coat the back of a wooden spoon. Fold in leftover chicken, pasta, vegetables or fish, spread the mixture in a dish, top with grated cheese and reheat till brown and bubbling.

Cheapskate cuisine is easy. So crack out the celery tops, tape down the lid of your bin, and get cooking. 

Picture credit: bazzadarambler/flickr (top); L-plate big cheese/flickr

(Elizabeth Luard is a Glenfiddich award-winning food writer and author. Her new memoir "My Life As a Wife" is published by Timewell.)