Thoroughly mix together the cornstarch and sugar. Combine raisins, sugar-starch mixture with sourcream, buttermilk, salt and spice in a saucepan and stir until well blended. Bring to a boil and cook until thick, 2-3 minutes. Remove from heat.
Beat egg yolks and milk together and add to hot mixture, stirring briskly. (save egg whites for a meringue)
Return to heat and cook until thickened, stirring the mixture while it cooks. (about 2 minutes)
Prepare meringue. Beat 3 egg whites and 1/4 tsp. cream of tartar until foamy. Beat in 6 T. sugar, one tablespoon at a time, until stiff and glossy. Beat in 1 tsp. vanilla.
Pour hot mixture into a baked 9" pie shell and cover with meringue. Bake in a slow oven (325-350 degrees, 15-20 minutes) until meringue is a golden brown. Remove from oven and cool before cutting.