9" baked pie shell
1 c. sugar
1/4 c cornstarch
1 tsp. unflavored gelatin
3 egg yolks
1 c. milk
1/4 c. butter
1/2 c. key lime juice
1 (8 oz.) carton sour cream

In saucepan, combine sugar, cornstarch and gelatin. With wire whisk, beat egg yolks with milk. Stir into gelatin mixture. Let stand 1 minute to soften. Cook over medium low heat, stirring constantly until mixture thickens and boils. Boil 1 minute. Remove from heat. Stir in butter, then lemon juice. Refrigerate 45 minutes. Fold in sour cream. Spread in baked shell. Chill. Serve with whipped topping, if desired.