Cut the fennel fronds off the large fennel and set 10 aside

Cut the stalk end off the fennel bulbs and slice thinly using a mandoline or sharp knife

Place the fennel, chilli, vinegar, water, fructose, zest, seeds, peppercorns and salt into a large stainless steel sauté pan

Bring to a simmer over a medium temperature, stirring until the fructose has dissolved

Simmer for 5 minutes and then remove from the heat

Allow to cool before placing the fennel into a sterilised glass jar

Pour as much liquid into the jar as will fit, up to 1cm from the rim

Tap to remove the air bubbles, the top with the fennel fronds

Seal and store for at least 48 hours (and up to 6 months) in a cool, dark cupboard

Once opened, refrigerate and eat within 4 weeks