Right, right, get on with it, I hear you saying. Enough with the history lesson. Where’s the recipe?
Sugar (amount to be determined by the amount of quince)
Ground cardamom or black pepper, if desired
Quarter and core the quinces, but do not peel them. Weigh them, then put them in a large, non-reactive pot.
Weigh out sugar in a ratio of 1:1½ with the fruit (that is, one pound of sugar to every 1½ of fruit). Add to the pot.
Add enough cool water to just cover the fruit. Bring the pot to a boil over medium heat, stir, then turn the heat down low and cover the pot. Let simmer until the fruit is soft enough to pierce easily with a fork. The quinces will probably have turned red by this time; do not be alarmed. The change in colour is perfectly normal.
Lift the fruit out of the syrup and force through a food mill or a sieve back into the pot.
Note: Please do not try to skip the sieve or food mill use here. Trying to use an immersion blender or a food processor will not make you a clever time saver. The purpose of the sieving is not merely to puree the fruit but also to remove the skins. An immersion blender or food processor will leave you with shreds of quince skin in your marmalade; trust me when I tell you that you do not really want that.
When all the fruit has been sieved and returned to the pot, stir and add the spices if you are using them. I usually use ½ teaspoon spice per pound of fruit, but you may adjust the quantity to your liking.
At this point, I usually have something like applesauce in consistency. You may wish to cook your marmalade, uncovered, until it reduces a bit more (Palladius says to cook until it is reduced by half but let your preference be your guide). I prefer mine a bit soft, and usually put it up in glass canning jars. If you want to do this, but are not an experienced canner, I recommend visiting the National Center for Home Food Preservation's jams and jellies page for a useful guide to the process.
You could also package the marmalade into small containers and freeze it.
I should note that at this point -- when the marmalade is safely jarred and processed, and any leftovers refrigerated or frozen -- I usually find it best to let it cool and rest a day or so before eating very much of it. The fresh marmalade is too fragrant, too much like eating a spoonful of perfume, especially if you've added cardamom. After a few days, it mellows. I like a spoonful stirred into a bowl of porridge. You can also spread it on bread or toast, or put a little alongside cold meat (goose or duck would be ideal. Chicken or turkey would be good also; I am meaning to try it with lamb sometime).
If you like, you can continue reducing the marmalade, stirring often, until it forms a thick paste -- what in Spain is called membrillo, in France cotignac, or in 19th-century English cookbooks, ‘quince cheese.’ The paste, when cooled, can be cut into shapes for serving. It goes well with dairy-based cheese. The traditional way to serve membrillo in Spain is with manchego cheese; another, similarly tangy cheese would also pair well with it.