Preheat oven to 350 degrees F.
Grease 1 or more cookie sheets. Using an electric mixer, cream together butter, shortening, and sugar in a bowl until fluffy. Add egg and beat until mixture is light in color.
Sift together flour, baking soda, salt, baking powder, ginger, nutmeg, cinnamon, cloves, and allspice; stir into creamed mixture. Fold in oatmeal, raisins, walnuts, and vanilla, blending well. Drop by rounded teaspoons onto cookie sheet. Bake for 12 to 15 minutes. Drizzle with Brown Butter Icing.
In a small saucepan heat butter over medium heat until golden brown, stirring occasionally. Remove saucepan from heat; stir in sifted powdered sugar and vanilla. Stir in enough water (2 to 3 tablespoons) to make an icing of drizzling consistency. Drizzle on warm cookies.