First, score the shells of the chestnuts. If you’re comfortable doing so, use a curved paring knife to cut a U-shape through the shell, being careful not to cut into the flesh of the nut: starting at the flat base, cut vertically up one of the narrow sides to the pointy top, then back down the other side to the base. Alternatively, use a sharp knife or kitchen scissors to cut or snip a cross the full length and width of the base of the shell.

Put the chestnuts in a saucepan and cover with boiling water from the kettle. Simmer for 10 mins, then turn off the heat. Lift the chestnuts out one at a time using a spoon, then peel off both the outer shell and papery skin. (Rubbing with a dry tea towel can help remove the skin.)

Bring the sugar and 300ml water to the boil, stirring occasionally. Once the sugar has melted, scrape in the seeds of the vanilla pod (if using) and drop in the pod itself. Reduce the heat to a simmer and cook for 5 mins, then add the chestnuts and simmer for a further 10 mins. Turn off the heat, cover and leave for 24 hrs.

The next day, return the syrup to the boil and bubble for 1 min. Remove from the heat, cover and leave for 24 hrs. Repeat this boiling and soaking process twice more.

Heat the oven to 120C/100C fan/gas 1/2. Lift the chestnuts out of the syrup, one at a time, and transfer to a baking tray lined with baking parchment. Transfer the tray to the preheated oven, then immediately turn the oven off. Leave the chestnuts to dry in the oven with the door closed for 1 hr. If they’re still wet after this time, leave in a warm place until fully dry. Once dry to the touch, wrap in individual squares of parchment and store in an airtight tin. Will keep for up to two months in an airtight container.