In a medium saucepan, combine sugar, cornstarch and salt. Gradually stir in milk. Bring to a boil over medium heat, stirring constantly. Boil and stir for 1 minute. Remove from the heat. Add 1/2 cup of hot mixture into eggs; return to saucepan. Add sour cream and vanilla; beat with whisk until well blended. Place saucepan in a bowl of ice water for a few minutes to cool. Cover and chill. Serve sauce over berries. Variation: Strawberries or other fresh fruit may be substituted for raspberries.