Zest all of your lemons and pop the zest into a tall jar. Add the vodka and seal the jar, adding a layer of cling film for added security. For the next seven-ten days leave your lemon zest to steep and infuse in the vodka. Every day give your jar a gentle shake to disrupt the mixture slightly. Add your caster sugar to your boiling water, stir until the sugar is completely dissolved and then add this to your zest mixture (moving everything into a bigger jar if needed). Re-seal your mixture once combined and leave to steep and infuse for another seven days. Remember to shake your jar every couple of days during this period. After conducing a very important taste test (or three) strain your mixture into a jug ready to poor into bottles.Make sure your bottles are clean and sterile and have a good stopper or seal to them. Divide your mixture between the bottles.We like to decorate our bottles with a disc of dried lemon and brown paper tag, but try improvising with stamps, ribbon or gift cards attached.