Preheat the oven to 150ºC . Combine half cup of the sugar with the salt, cinnamon, cornstarch and cocoa in the top of a double boiler. Blend in the cold milk.Stir in the hot milk and cook over hot water until thick, about three to five minutes, stirring constantly. Cover and continue cooking until very thick, about eight minutes, stirring occasionally. Add the butter. Beat the egg yolks lightly and blend them with the remaining half cup sugar. Add a little of the hot mixture, then stir into the remianing hot mixture.Cook, uncovered, over hot (not boiling) water until very thick, about ten minutes. Add the vanilla. Cool.Turn the mixture into the baked pie shell. Top with meringe and bake twenty minutes. MERINGUE: Combine three egg whites with 0.125 tsp salt and beat until the whites stand in soft peaks. Beat in four Tbl sugar, one Tbl at a time, until stiff.