Sorry, that was marking place to come back to this. I hate my iPad for posting on!
I can't link to the original recipe, but iPad errors above can be fixed. Giving full credit to PigletWillie:
Lemoncello – Pigletwillie’s Pukka 80 Day version
True Limoncello is made in Sorrento, from lemons whose trees overlook the Mediterranean. However, if you have good lemons, it’s not difficult.
INGREDIENTS:
• 15 thick-skinned lemons
• 2 bottles (750 ml each) of the best 100 proof Vodka or a 750 ml bottle of 190-proof alcohol
• 4 1/2 cups (1 k) sugar
• 5 cups (1.2 litres) water if you use vodka, or 8 (2 litres) if you use grain alcohol
PREPARATION:
Wash the lemons in hot water before you start. Remove the peel with a vegetable peeler, removing all white pith on the back of the peel by scraping with a knife, and put the peels in a demijohn. (PW adds the juice as well).
Add 1 bottle of Vodka, or half the alcohol, and stir. Cover the jar, date it, and put it to rest in a dark cabinet at room temperature.
After 40 days, take out the lemon-Vodka mixture. In a sauce pan set over high heat, stir the sugar and water together and boil for 5 minutes. Let the sugar syrup cool completely in the pan, about 10 minutes. Add the sugar syrup to the lemon-Vodka mixture along with the second bottle of Vodka or the remaining alcohol.
Stir well to combine. Replace the demijohn bung and note the finish date. Return it to the dark cabinet and store for 40 more days.
At day 80, remove the limoncello from the cabinet. Strain the mixture and discard the lemon peel.
Pour into clean, unused bottles with caps or decorative corked bottles. Store the bottles in the pantry, but put one bottle at a time in the freezer until ready to use.
Makes approximately 3 litres.
My own version, having adapted through "oops, I forgot to read the recipe properly" accidents, is to basically peel 15 lemons using a potato peeler to get the zest off them. Then squeeze those same lemons and put juice and zest together into a large kilner (I have a 3l one). Usually get about 750ml of juice. I add a good dollop of sugar at that point - probably 500g or so. And add in one full bottle of vodka, 750 ml (or is it 700? Standard bottle). Shake together, and put in dark cupboard. Shake daily for a couple of weeks until sugar is dissolved. Check flavor - add more sugar if needed (should be very lemony but not too bitter - think of the San Pellegrino limonata drink or that kind of "proper" lemon lemonade) - remember to keep shaking once a day until all sugar is dissolved. Ignore for as long as possible in the dark cupboard - at least 45 days and preferably up to 3 months. Strain out the zest, and if you have a muslin to strain through, it takes a lot of the "bits" from the juice too. Check flavor - add more sugar if needed, which I would tend to do as a sugar syrup at that point (melt the sugar in some water and allow to cool). Bottle into clean, sterilised jars. Serve very cold. Keeps a long time if you want to. I have almost never added water - but would often dilute the final version with (lots of) 7up as a long drink, as often as drinking it neat in small (SMALL) servings.