Leftover mash I fry into cakes

There is a bowl of mash in the fridge from last night's supper, with a dry crust on top. Warmed up as mash, it never tastes the same. It goes stiff, a little grey at the edges, and the bowl comes back to the kitchen half full. So I stopped reheating it. Now leftover mash goes into a pan as small golden cakes, and the same bowl that nobody wanted becomes breakfast, or a side for a quick supper.

The trick is that the mash must be cold. Warm mash is soft and sticky and falls apart in the pan. Cold mash from the fridge holds a shape in the hands, and that is exactly what I need. I tip it into a bowl, break the dry crust off the top with a spoon if it has gone hard, and look at what I have. A good bowl of about 500 g makes eight small cakes, enough for two hungry people or four as a side.

I add one egg, two tablespoons of plain flour, a pinch of salt and pepper, and whatever is in the fridge that suits potato: a few chopped spring onions, a spoon of grated cheese, a little chopped dill or parsley. In autumn I sometimes add a spoon of leftover roast pumpkin or a little cooked cabbage. I mix it with a fork, not a whisk, just until it comes together. If it is still very wet, I add one more spoon of flour, but no more. Too much flour makes the middle heavy and doughy, and the outside browns long before the inside is properly hot.

Then I wet my hands with cold water and shape the cakes on a floured board, each one about the size of my palm and as thick as a finger. Wet hands stop the mixture sticking, and a light dusting of flour on each side helps the crust. I press them flat with my fingers, rather than rolling balls, so they cook evenly.

The pan goes on a medium heat with a thin layer of sunflower oil. I wait until the oil shimmers, then lay the cakes in with space between them. If I crowd the pan, they steam instead of frying, and the crust never comes. I leave them alone for about four minutes. This is the hardest part, because I always want to lift one and look. When the edge underneath is deep golden, I turn each cake once with a thin spatula and give the second side the same time. Then I turn the heat down a little for another two or three minutes so the middle heats right through.

Food safety matters here, because this is a leftover. Cooked potato should be cooled quickly and put in the fridge within two hours of cooking, covered. I use leftover mash within two days, and I only reheat it once, so the cakes are the one and only reheat. They must be steaming hot all the way through before they reach a plate: I break one open in the middle to check. If the mash smells sour or looks slimy, or I can't remember when it was made, it goes in the bin, not the pan. The cakes contain egg, milk (from the mash) and wheat flour, so I say so when someone at the table has an allergy. Without the flour, they hold together less well, but a spoon of potato starch works for a wheat-free version.

We eat them with a fried egg and a spoon of soured cream in the morning, or next to sausages or a piece of fish in the evening. With a bowl of soup and some pickles, they are a whole supper. If you like the crisp potato cakes we make from raw potato, my classic potato draniki are a different dish but the same kind of comfort, and the fried potato pies use up mash in another way.

A cold bowl of mash is not a failure. It is the start of something better than the first meal. Do you make anything with leftover mash, or does it usually end up in the bin?

How to make potato cakes from leftover mash. Makes 8. About 20 minutes. You need 500 g cold leftover mash, 1 egg, 2 tbsp plain flour plus extra for dusting, salt and pepper, chopped spring onion or herbs (optional), sunflower oil for frying. Mix the mash, egg, flour and seasoning; shape 8 flat cakes with wet hands; dust with flour. Fry in hot oil for about 4 minutes a side, then 2–3 minutes on a lower heat, until golden and steaming hot in the middle. Eat straight away.