1. Cut the lemons and oranges in half lengthwise. Cut each half into 3 wedges, then slice across the wedges in 1/2cm slices.

2. Place the citrus in a large, heavy-bottomed pot, cover with cold water and leave the pot covered on the stove overnight. The next day, bring to the boil over a high heat. Cook until the peels are very soft and fully cooked, about 20 to 30 minutes. Top up with water if it drops below the level of the peels.

3. Add the sugar to the pot and stir to combine. Turn the heat up to high and bring back to the boil. Lower the heat to medium and let the marmalade simmer until set. It should take about 30 minutes, but start checking after 15 minutes, by spooning a little onto a chilled plate that has been placed in the freezer. If it looks firm like jam, it's ready.

If you are using a sugar thermometer, it should be at 105 degrees.

4. Allow the marmalade to cool to room temperature before serving. Store leftovers in the fridge and use within a month.

• Use this marmalade in Frank Camorra's steamed pudding recipe