Prepare pie plate.
Spray non-stick cooking spray in pie plate and wipe out excess.
Dust with cornstarch.
Combine egg whites, salt and cream of tartar.
Beat until very stiff.
Beat in sugar gradually, until peaks are formed.
Gently fold in walnuts.
Spread in prepared pie plate on the bottom and up the sides, making room to add the chocolate filling later.
Bake in preheated 250° oven for 50 minutes, until golden brown and dry.
DO NOT REMOVE FROM OVEN.
Turn oven off. Leave oven door closed and let cool to room temperature.
Remove from the oven and store tightly covered at room temperature until ready to fill.