• 1.8 kg (4 lb) fresh chestnuts
• 500 g (1 lb. 2 oz/2¼ cups) caster (superfine) sugar
• 2 lemons
• 1 vanilla bean

Take each chestnut and, using a small sharp knife, make a cross-shaped incision in their flat side. Bring a large saucepan of water to the boil and blanch the chestnuts for 3 minutes. Remove from the heat and leave the chestnuts in the water. Using the blade of the knife, remove the outer skin. Remove the inner skin using a knife, or wipe it off with a clean cloth — the ease of removing the skin will depend on the age and variety of chestnut. Discard the skins.

Put the sugar in a large saucepan with 1 litre (35 fl oz/4 cups) water. Using a vegetable peeler, remove the lemon zest in wide strips and add these to the pan. Cut the vanilla bean in half lengthways, then scrape the seeds into the pan. Discard the vanilla bean (or reserve for making vanilla sugar, if desired).

Bring the liquid to the boil over high heat and cook for 5 minutes. Add the peeled chestnuts. When the liquid starts to boil again, reduce the heat to medium and simmer for 20 minutes.

Meanwhile, wash and sterilise two 1 litre (35 fl oz/4 cup) preserving jars and their lids and seals. Making sure the jars are still very warm, remove the chestnuts from the heat and transfer to the jars using a sterilised slotted spoon, filling the jars evenly. Pour in the syrup and seal while still hot. Allow to cool, then store in a cool, dry place for up to 3 months. Once opened, the chestnuts will keep, refrigerated, for 2–3 weeks.