In a large saucepan combine sugar and gelatin. Stir in half-and-half or light cream. Cook and stir over medium heat until mixture almost boils and sugar dissolves. Remove from heat. Stir about 1 cup of the hot mixture into beaten eggs; return all to saucepan. Cook and stir for 2 minutes or until slightly thickened. Do not boil. Stir in instant coffee crystals and whiskey or liqueur. Cool. Transfer the mixture to a 4-quart ice-cream maker and freeze according to the manufacturer's directions.

Or, transfer the mixture to a 9x9x2-inch baking pan. Cover and freeze 2 to 3 hours or until almost firm. Break frozen mixture into chunks. Transfer to a chilled bowl. Beat with an electric mixer until smooth but not melted. Return to pan. Cover; freeze until firm. Makes about 1-1/2 quarts (12 to 16 servings).

Place ice cream in freezer container; seal, label, and freeze up to 1 week.