In a small bowl, soak currants in 1/2 cup of hot water until swollen; drain and set aside. Preheat oven to 400 degrees F (200 degrees C). Grease cookie sheets.
In a large bowl, cream together the shortening and brown sugar until smooth. Beat in the eggs, one at a time, then stir in the 1 teaspoon vanilla.
Combine the flour, baking powder, baking soda and salt, stir into the creamed mixture alternately with the buttermilk. Fold in the chopped walnuts and dried currants. Drop by rounded spoonfuls onto the cookie sheets.
Bake for 8 to 10 minutes in the preheated oven. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely. When the cookies are cool, frost with the brown butter frosting.
To make the frosting: Melt butter in a small saucepan over medium hat until golden brown. Stir in the 1/4 cup of water and 1/2 teaspoon vanilla. Beat in the confectioners' sugar 1/2 cup at a time until icing is of a spreadable consistency.
