In top part of double boiler mix cornstarch, 3/4 cup sugar, and salt.
Stir in milk.
Cook over hot water, stirring constantly, until thickened.
Pour over eggs, mixing thoroughly.
Put lemon juice, 1/2 cup sugar, and avocado pulp in blender.
Blend for a few seconds.
Combine with custard; add cream.
Add a few drops of green coloring.
Pour into crank-type freezer and freeze until firm.