Here is the process that can be used to make this. True Limoncello is made with high alcohol spirits and very specific lemons in Italy but this turned out well. I made it with differing qualities and proofs of vodka and did not consider the differences substantial to the final taste.
Limoncello recipe Rev 1
Starting point:
750 ml 100 proof vodka: Jacquins or any inexpensive brand is acceptable (100 proof is preferred, 80 proof will make just a lighter alcohol Limoncello.) 375 grams (1 2/3's cup) table sugar (cane or beet, it does not matter) 7 medium lemons, good color.Procedure: Zest lemons, if you are removing more than 2.5 g per medium lemon you are probably taking off too much pith with the zest. You should end up with about 18 g +/- 10%. A fine cheese shredder makes a good zesting tool. The goal is to take off the outer surface of the lemon; if the remaining 'pith' (outer covering) is white, too much has been removed; a pale yellow pith should remain. Pith will impart a bitter taste to the end product. The lemons can be juiced and the juice frozen for another purpose; it is not used in Limoncello.
Add the zest to the vodka and let it steep several days at room temperature (at least 65F); a week is fine. Once you see good color you have probably extracted enough oil from the zest. The zest will start to lose its color; it will not get to white but will become a pale yellow. If you want to experiment with steeping times pull off a known quantity of liquid, add sugar (1/2 the amount of liquid) shake until dissolved and taste. (I.E. 50 ml liquid to 25 grams of sugar.)
Remove the zest from the liquid; pour it through a coffee filter if preferred.
Optional: Fine with hot mix Sparkolloid at a rate of 1 g/gallon (US) and rack when clear. This will give a clear end product. This step requires the liquid be at room temperature, the fining agent is not effective at cool or cold temperatures. Commercial Limoncello is often cloudy; this step is only for aesthetics.
Add the sugar and stir or shake until dissolved. It will not look like it is possible to dissolve this much sugar, but it is possible. Just shake it up, let it settle repeat until all of it is dissolved.
Serve chilled preferably but the amount of sugar added makes this smooth tasting at any temperature.
The amount of zest used, amount of sugar added and steeping times are variable by personal preference; the only hard and fast rule is the strength of the vodka and that is not necessarily hard and fast either. I have made it both ways and liked the end result of both. Joe