Wash the lemons well with a potato scrubber and zest them (remove the outer peel) with a vegetable peeler or a small knife to preserve just the yellow portion of the peel. Remove as much of the bitter white pith as you can and deposit the peels into your jar. Add half of the bottle of vodka and seal. Store the jar in a cool, dark place for 10 to 40 days (the longer, the better. Obvi).
After your initial infusion period, combine the sugar and water in small saucepan and cook over a medium heat for 10 minutes, stirring occasionally. Once your simple syrup has cooled add it to your jar and keep it in the dark for another 10 to 40 days.
After your second infusion period, strain your limoncello through a mesh strainer, or a cheesecloth if you have one, and return it to your bottle and chill in the freezer. Serve cold in teensy, tiny glasses.