Sift cream of tartar and sugar together. Add, 2 tablespoons at a time, to egg whites, continuously beating.
Grease a 9" pie pan. Spread the crust mixture in the pan. Bake at 300° for 1 hour.
For filling, melt the chocolate chips with the sugar and milk in a double boiler. Add 3 egg yolks, one at a time and beat. Add vanilla. In a separate bowl, beat 3 egg whites until stiff. Fold the beaten egg whites into the slightly cooled chocolate mixture. Place the mixture into the prepared pie crust; refrigerate.
Top with whipped cream when ready to serve.