Sift dry ingredients and set aside. Cream butter and brown sugar, add eggs, vanilla, orange rind and sour cream. Stir in dry ingredients, blending well. Add nuts. Drop by teaspoonful onto lightly greased cookie sheet. Bake at 350° for 12-15 minutes. Top with frosting while still warm. About 5 doz. Frosting: Combine all ingredients, beating well until spreading consistency. Place 1/4 teaspoon frosting on each cookie.