Blend butter, brown sugar and sifted dry ingredients with pastry blender as for pie crust. Add egg and mix thoroughly. Stir in walnuts.
Drop thin batter by half teaspoonfuls about 2" apart onto heavily greased baking sheet. (Cookies spread during baking.) Bake in moderate oven (375°) 5 to 6 minutes. Remove from baking sheet at once and cool on racks.