1. Measure flour, salt, and soda into a sifter.
2. Beat the 1/2 cup shortening with brown sugar until fluffy in large bowl with electric mixer at high speed; beat in egg and vanilla. Sift in flour mixture, blending to make a soft dough.
3. Stir in crushed corn flakes, rolled oats, and butterscotch-flavored pieces. Spread half of the mixture evenly over bottom of a greased 9x9x2-inch baking pan.
4. Melt chocolate pieces with the 1 tablespoon shortening in top of a double boiler over simmering water; remove from water. Stir in walnuts and sweetened condensed milk. .
5. Spread over layer in pan, then spread with remaining butterscotch mixture.
6. Bake in moderate oven (375°) 40 minutes, or until firm and golden. Cool completely in pan on a wire rack. Cut into 36 squares.