• Wash 10 whole lemons thoroughly to remove any wax or residue. Pat them dry.
• Remove the zest (just the yellow part with as little white part as possible as it’s bitter) using a vegetable peeler or sharp kitchen knife. Place the strips of lemon zest in a large, clean glass jar with glass or plastic lid, not metal if possible. See Notes below.
• Split 1 vanilla bean or 2 teaspoons pure vanilla extract or vanilla pastelengthwise and add it to the jar (or add 2 teaspoons pure vanilla extract or vanilla paste later).
• Pour in 750 ml high-proof vodka or grain alcohol, seal the jar, and shake gently.
• Store in a cool, dark place for 3 or 4 weeks, shaking occasionally.

Make the simple syrup:

• In a saucepan, combine 2 ½ cups granulated sugar and 2 ½ cups water. Stir over medium heat until the sugar is dissolved. Let the syrup cool to room temperature.

Finish the limoncello:

• Strain the infused alcohol through a fine-mesh sieve or cheesecloth into a clean container, discarding the lemon zest and vanilla bean.
• Stir in the cooled simple syrup (if using vanilla extract or paste, add it now).
• Pour the limoncello into a bottle and seal it.
• Let it rest in the refrigerator or freezer for at least 1-2 weeks to allow the flavors to meld. After that, keep refrigerated or frozen (my choice).
• Serve chilled in small glasses.