Preheat oven to 350. Lightly grease a 9x13 cake pan. Sift together the first 6 ingredients. In a separate bowl, mix eggs and sugar until smooth. Stir in pumpkin and oil and mix thoroughly. Add flour mixture and stir until just combined. Fold in nuts. Pour cake batter into greased pan and bake 35-45 minutes or until a toothpick comes out clean. Turn cake out onto rack and let cool.
Frosting: With an electric mixer, beat softened butter and cream cheese until smooth and fluffy. Add brandy and syrup. Slowly add powdered sugar until frosting is thick enough to spread.
Spread frosting over cooled cake and garnish, if desired, with coarse sugar or additional chopped nuts.