Put 4 cups milk in double boiler. Measure 1/2 cup milk in small bowl. Add 4 egg yolks; beat well. Combine 4 tablespoons cornstarch (level), 2 cups sugar and 1 teaspoon salt. Add egg and milk mixture to dry ingredients and blend. Stir into hot milk, and add 2 tablespoons butter and 1 1/2 cups cooked raisins. Boil until thickened. Add 1 1/2 teaspoons vanilla. Pour into 2 baked pie shells. Top with meringue or whipped cream.