You can make your own limoncello from the following recipe! It is very strong and best served in very small glasses.
Two fifths of 100 proof vodka
4 cups sugar
5 cups water
Zest of 15 fresh lemons
Wash the lemons with a vegetable brush and hot water to remove any residue of pesticides or wax. Carefully zest the lemons with a zester or vegetable peeler so there is no white pith on the peel.
In a 1-gallon glass jar, add one fifth vodka and the lemon zest. Cover the jar and let sit at room temperature for at least 30 days in a cool dark place.
In a large saucepan, combine the sugar and water and cook until thickened, approximately 5 to 7 minutes. Let the syrup cool before adding it to the limoncello mixture. Add the additional fifth of vodka. Allow to rest for another 10 to 20 days.
After the rest period, strain and bottle, discarding the lemon zest. Keep in the freezer until ready to serve.