Peel and pit the avocado. Place the avocado into the bowl of a stand mixer fitted with the whisk attachment along with the lemon juice and beat until lightened in color, approximately 2 to 3 minutes. Add the powdered sugar a little at a time and beat until smooth. Add the lemon extract and mix to combine. If not using right away, store in the refrigerator.
Recipe courtesy of Alton Brown, 2005