Take each chestnut and, using a small, sharp knife, make cross-shaped incisions in their flat sides. Bring a large saucepan of water to the boil and blanch the chestnuts for three minutes.

Remove from heat and leave the chestnuts in the water. Using the blade of the knife, remove outer skin. Remove the inner skin using a knife, or wipe it off with a clean cloth (the ease of removing the skin depends on the age and variety of chestnut). Discard skins.

Put the sugar in a large saucepan with 1 litre of water. Using a vegetable peeler, peel lemon zest from the lemons in wide strips and add it to the pan.

Cut the vanilla bean in half lengthways, then scrape the seeds into the pan and discard the vanilla bean. Bring the liquid to the boil over a high heat and cook for five minutes.

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

Meanwhile, wash and sterilise two 1-litre preserving jars, lids and seals.

Making sure the jars are still very warm, remove the chestnuts from heat and transfer to the jars using a sterilised slotted spoon, filling the jars evenly. Pour in syrup and seal while hot.

Allow to cool, then store in a cool, dry place for up to three months.

Once opened, the chestnuts will keep, refrigerated, for two to three weeks.

Serving suggestion: Enjoy with Frank Camorra's crepes and orange cream.

FRANK'S TIP

Buy the best-quality chestnuts; lesser-quality nuts will taste grainy and will not cook well in the syrup. Look for smaller rather than large chestnuts.