Mix crushed wafers and butter together and pat into a buttered 8 x 11-inch cake pan. Chill.
Soften gelatin in cold water and set aside. In top of double boiler combine eg yolks, sugar, salt, and milk. Add custard to gelatin mixture and cool. Fold stiffly beaten egg whites, whipped cream, and vanilla into gelatin-custard mixture. Pour into crust. May be garnished with additional cookie crumbs. Chill for several hours before serving.