Preheat oven to 375 degrees F. Grease cookie sheets. Set aside.

In a medium mixing bowl stir together flour, salt, baking soda, and baking powder. Set aside.

In large mixing bowl beat the brown sugar and shortening with an electric mixer on medium speed until well mixed. Add eggs and 1 teaspoon vanilla. Beat until well mixed. Add flour mixture and sour cream alternately to beaten mixture, beating after each addition.

Drop dough by rounded teaspoons 2 inches apart onto prepared cookie sheets. Bake for 10 to 12 minutes or until edges are lightly browned. Transfer to a wire rack and let cool.

To make frosting, in a medium saucepan heat and stir 1/2 cup butter (no substitutes) over medium-low heat until golden brown. (Do not scorch.) Remove from heat.

Stir in powdered sugar, boiling water, and 1-1/2 teaspoons vanilla. Beat until frosting is easy to spread.

Immediately spread on cooled cookies. If frosting begins to set up, stir in a small amount of additional boiling water. If desired, top with additional chopped walnuts or walnut halves.