Put the zest into a large jar and top up with vodka
Seal the jar and store in a dark cupboard for 20 days for the deepest colour and flavour - or if you can't wait and don't have that much patience then place in a sunny place for 8 days
After the Limoncello has steeped, strain the vodka and set aside
Prepare a sugar syrup by bringing the water to a simmer in a saucepan, then stirring in the sugar to dissolve
Allow sugar syrup to cool
Mix the sugar syrup with the infused vodka, stirring gently
Taste and add additional sugar syrup if desired
Bottle the limoncello and chill in the fridge for up to a month or the freezer for up to a year
Only use ripe lemons - make sure yours don't have any green on the skin
Be careful not to include any of the white pith underneath the lemon rind when peeling off the zest
Notes
To keep the limoncello as cold as possible, leave your shot glasses in the freezer until you're ready to serve.