We were traveling through Italy several years ago where I met Vinnie, from Naples, who gave me the following recipe for Limoncello:
2 liters vodka 1 kilogram sugar
20 lemons 1 liter water
A) Peel the lemon, slice and put all the slices into the vodka. Wait for 15 days.
B) After the two weeks, take off the lemon slices from the vodka and filter.
C) Boil the water and when it reaches boiling, add the sugar. Simmer for 1/2 hour. Remove from heat and let cool.
D) When the syrup is cool, add to the vodka and let steep in the bottle for a week.
E) Filter once again and drink very cool.
I have found that you can make a more full-bodied limoncello by leaving the peel on the lemon. Also, I wait 3–4 weeks before straining out the slices and then let the limoncello age for several months before drinking. I put the liquor in 1/2 gallon Ball Glass Canning Jars and then place jars in paper bag and set aside in a dark, cool closet.
You can make the sugar syrup more tart or sweeter, according to your taste, just by adding more or less sugar. This is something I experimented with and make it according to my husband's taste which tends to be toward the tart side. At first, you may want to divide the lemon vodka into three batches, and then when it's time to add the syrup, make three different syrups with various amounts of sugar to see which suits your taste. I marked each jar so that when it was time to taste, I could record the results.
The lemons come from COSTCO and so does the vodka!
We use it as a digestive aid after a monster feast and I must say, it does get rid of indigestion quickly!