Heat oven to 325 degrees.
Beat margarine and sugar until light and fluffy.
Beat in eggs and vanilla.
Mix in flour, baking powder and salt.
Stir in chocolate and walnuts.
Shape dough into 2 slightly flattened logs onto greased and floured cookie sheet 2 inches apart.
Bake 25 minutes or until lightly browned.
Place on cutting board, cool 5 minutes.
Using serrated knife, cut log into slices about 3/4 inch thick.
Place slices upright on cookie sheet ½ inch apart.
Bake 10 minutes more or until slightly dry.