Crust: mix flour, powdered sugar, and butter with pastry blender until crumbly. Press firmly into a ungreased 13X9 pan and bake at 375° for 14 minutes or until golden. Remove from heat.
Topping: sprinkle morsels and 1 cup nuts over the hot crust.
Beat egg whites with mixer until frothy. Gradually add brown sugar. Beat until stiff peaks form. Spread meringue over morsels and nuts. Sprinkle with remaining nuts. Bake at 375° for 15 minutes or until golden brown. Serve warm or cool.