For the custard filling, combine its 6 ingredients in saucepan and cook over medium heat, stirring constantly until thick. Set aside to cool. Preheat the oven to 325 degrees.
For the graham cracker crust, combine the 4 ingredients and mix thoroughly by hand. Measure 1/4 cup of this to set aside; form a crust of the remainder by pressing it evenly into the inside of a 9-inch pie pan.
For the meringue, use an electric mixer to beat the egg whites. Add cream of tartar and continue beating; gradually add the sugar and beat until the meringue has stiff peaks.
Pour the cooled custard into the pie crust. Top with the meringue, gently spreading it for an even covering. Spread the 1/4 cup of reserved graham cracker crust over the meringue.
Bake just long enough to brown the meringue. Let cool and serve, or refrigerate for later enjoyment.