Thoroughly wash the lemons (preferably organic).
With the use of a vegetable or potato peeler, remove lemon peel (avoid the white pith as this will make your limoncello bitter).
Place lemon peel in a mason jar (or another container with a tight-fitting lid).
Add alcohol, close tightly, and let steep for at least 6 days or up to 40 days in a cool dark place. Swirl contents of the jar twice a day.
Remove lemon zest (should be a pale color- the alcohol on the other hand should be a bright yellow).
Strain with a cheesecloth in a clean bottle.
In a large saucepan, over medium-low heat, warm the milk, sugar and vanilla bean.
Whisk frequently until the sugar is dissolved.
Remove from heat and allow to cool to room temperature before adding to alcohol.
Strain (with the help of a cheesecloth) in a decanter with alcohol.
Refrigerate or freeze until ready to use.
