Preheat the oven to 350. Grease 1 or more cookie sheets.
Using a mixer, cream the butter, shortening and brown sugar. Add the eggs and beat until the mixture is light in color. Add the buttermilk.
Sift together the flour, baking soda, salt, baking powder, ginger, nutmeg, cinnamon, cloves and allspice in another bowl; stir the dry ingredients into the butter mixture. Fold in the oatmeal, raisins, walnuts and vanilla. Drop by heaping teaspoonfuls, 2 inches apart, onto cookie sheets. Bake until lightly browned, 12 to 15 minutes.
Meanwhile, prepare the icing: In a small saucepan, heat the butter over medium heat until golden brown, stirring occasionally. Remove from the heat; stir in the confectioners' sugar and vanilla. Stir in enough water (3 to 4 tablespoons) to make the icing drizzling consistency. Drizzle on the warm cookies.
Recipe courtesy Paula Deen for Food Network Magazine