Preheat oven to 350 degrees.
Grease and flour 2, 9-inch round cake pans. Line bottom of the greased cake pan with a parchment round.
In a medium bowl, sift together flour, baking powder, baking soda, salt, cinnamon, nutmeg, cloves and allspice.
In a large bowl, using a hand or stand mixer, cream together shortening, brown sugar and white sugar until light and fluffy. Add eggs, one at a time, and mix well until combined between each addition. Add vanilla and stir to combine.
Alternating between dry ingredients and buttermilk, add in 1/3 of the flour mixture and mix until just combined. Add 1/2-cup buttermilk and stir to combine. Add 1/2 the remaining flour mixture and stir. Add 1/2-cup buttermilk and stir to combine. Add remaining flour and stir. Add remaining buttermilk and stir to combine. Stir in chopped walnuts.
Divide batter between prepared pans. Bake in preheated oven 35 to 45 minutes, or until a toothpick inserted in the center of the cake comes out clean. Remove from oven and place on cooling rack, in pan, to cool for 10 minutes. Turn cakes out of pan and let cool completely on cooling racks before frosting.
For the Frosting:
In a medium bowl, using a hand or stand mixer, beat butter and cream cheese until light and fluffy. Add confectioner's sugar and maple syrup and stir to combine. If frosting is too thin, add additional confectioner's sugar. If too thick, add milk a tablespoon at a time until spreading consistency.