In a small saucepan, combine sugar and flour. Gradually whisk in pineapple juice. Add butter. Cook and stir until butter is melted and mixture comes to a boil. Cook and stir for 1-2 minutes or until thickened.
Remove from the heat. Stir a small amount of hot mixture into egg; return all to the pan, stirring constantly. Bring to a gentle boil; cook and stir for 1 minute. Remove from the heat. Cool to room temperature, stirring several times.
Fold in whipped cream. Cover and refrigerate for at least 1 hour. Serve with fruit.