From The Nero Wolfe Cookbook by Rex Stout:

3 large ripe avocados
1 C sugar
4 T lime juice
2 T green Chartreuse
1/2 C heavy cream
6 slices lemon

Chill avocados, cut in half, remove pulp and reserve skins.
To the pulp add sugar, lime juice and Chartreuse, whip to a
smooth consistency. Return mixture to the skins, garnish
with a lemon slice, whip the cream and serve on the side.