If you can get quinces in reasonable numbers, membrillo is a wonderful way of rounding off a meal – to be eaten with a hard, salty cheese such as Manchego, Pecorino or Parmesan. It can also be cut into cubes, coated with icing sugar and treated like Turkish delight. Or whisk it into gravy to go with roast game birds, or stir it into a fruit crumble for an added depth of sweet fruitiness. The cheese is best left for a few weeks to mature before it's eaten.
Put the quince in a pan with 300ml water. Cover and cook very gently until tender – you may have to mash it a bit towards the end.
Push the cooked fruit through a sieve or a mouli-légumes to make a purée. Measure the purée in a measuring jug and then put it in a deep, heavy-bottomed saucepan. For each litre of purée, add 550g granulated sugar. Heat very gently, stirring occasionally, until the sugar is thoroughly dissolved.
Then raise the heat to bring the mixture to the boil and cook until thick. It will become a darker red and start popping as it leaves the sides of the pan. The trick is to stir continuously with a heavy wooden spoon so it never catches and burns. As it reduces you will need to protect your hand with a tea towel or oven glove.
Once you can hardly move the spoon, take the pan off the heat and transfer the mixture to a baking tray lined with baking parchment, spreading it out in a layer about 1cm thick. Leave it, uncovered, for a few days in a warm room or airing cupboard, or even in an oven on the lowest possible setting. Then cut it into cubes with a hot knife. To store, pack them in an airtight container, sprinkled with sugar.