Heat oven to 350. Line two 9" cake pans w/ parchment paper. In lg bowl, whisk together flour, cinnamon, ginger, nutmeg, allspice, baking soda, baking powder and salt. In another bowl, using mixer, cream 8 tbsp butter and sugar until fluffy. Beat in eggs. Wisk in pumpkin. It may look curdled, that's normal. Beat in flour mix, 1/2 of mix at a time until smooth. Fold in chocolate chips and nuts. Pour evenly into pans. Place pans in middle of the oven. Bake 35 min, or until a toothpick inserted in center comes out clean. Cool. Invert cake onto lg serving plate. Peel the parchment paper off the cake. In lg bowl, blend remaining butter, powdered sugar until smooth. Beat in chocolate and vanilla until smooth. Ice top of cake first. Place 2nd layer of cake on top of 1st layer of cake. Ice the top and sides of cake.