-In saucepan, stir buttermilk and sugar over medium heat just until milk is warm and sugar dissolved; remove from heat; add lemon juice and salt.
-Place Avocado in food processor; whirl until fairly smooth. Add warm buttermilk mixture; process until smooth. Transfer to mixing bowl; cover; place bowl over ice cubes or in refrigerator; chill at least 1 hour.
-Pour cold Avocado mixture into container of 1-quart ice cream freezer; process according to manufacturer’s directions. Spoon into bowl; cover and freeze until frozen, about 2 hours.
-Serve with fresh fruit and mint leaves, if desired. Yields 8 servings (about 1 quart).