This week I am

in the thick of making Seville orange marmalade. There is a tree in the back garden that was planted more than 30 years ago, when I had begun making marmalade and was alarmed by the thought that the oranges might not always be available commercially. The tree produces prodigiously, every year. I give oranges away - although fewer chefs know what to do with bitter oranges - and keep many in the cellar for use during the year. The juice is perfect whenever any recipe calls for orange and lemon juice; it is great for basting lamb; rather nice for basting roasting chicken; excellent in any sauce for duck.The recipe is simple, but it takes time and patience, and a large sharp knife. I allow 1.6kg Seville oranges, 4.2 litres of water, and about 2.8kg sugar. The juice of half a lemon is optional. Cut the oranges in half, squeeze out the juice, keep it to one side, and reserve any pulp and pips. Slice the orange halves into strips (quite narrow), then across into small diamonds or squares.Put the water into a large preserving pan. Add the peel, and orange juice. Put the pulp and pips into a square of muslin or Chux (pour over boiling water so there is no hint of flavour), tie up into a little bundle, and add the to the pan. Bring to the boil and boil until the peel is soft and about half the water has gone. Lift out the bundle and discard it. (The pips have lots of pectin and assist in the setting.)Add the sugar in two or three lots, stirring well. Bring to boiling point, and allow to boil (not too fast) until setting point is reached. Keep an eye on it always so that it a) doesn't boil over and b) doesn't burn. After about 15 minutes of boiling, add the lemon juice if desired, and then stay close and stir occasionally. You know when it's right because the bubbles change, and because there is resistance as you stir.Or you can use a sugar thermometer (jelly stage is what you want on the dial), or the time honoured test of placing a little on a saucer and putting it in the fridge quickly. If it sets on the saucer, and if it wrinkles a bit when you run your finger through it, it's right.Allow to sit for a few minutes before potting in sterlised jars.