Very carefully peel lemon peel into thin, long strips, doing your best to avoid getting pith with the outer peel. Use the lemons for another purpose or juice them and freeze the juice. If there is too much pith on the peels, take a spoon or butter knife and scrape it off. This is important as you don’t want a bitter flavor.
Place the peels and a vanilla bean, if using, into a large bottle and tuck away in a cool, dark, cupboard for at least 30 days, shaking the bottle occasionally.
Mix water and sugar together in a saucepan and cook over medium heat until the sugar has completely dissolved. Pour the sugar over the lemon/vodka mixture and allow to sit overnight. Strain the Limoncello through a mesh strainer or through cheesecloth and bottle. Allow the bottles to rest for another few weeks before using. Serve chilled.