Prepare a kilogram of quince purée by cutting each quince into four pieces, removing the seeds (do not dispose of the skin, since it contains pectin) and cooking in boiling water for 10 minutes. Purée the softened fruit through a colander or blender.
Cook it in a pan slowly for about an hour until it thickens. Add 80 decagrams of sugar and cook over a high heat, stirring constantly for about 10 or 15 minutes. At this point you can add walnuts, almonds, lemon or orange peel, vanilla, cinnamon, or cloves. Or add nothing.
Test its texture for hardening. When it is hard enough, spread it in a form or a dish to a depth of about the width of two fingers. Allow it to set for a day or two and then remove it from the form and cover with cellophane or aluminum foil and keep in a dry place.
It will keep for several weeks. However, you should turn it over every other day, since it moulds easily.
