Chocolate Pumpkin Cake

Preheat oven to 350°F. Grease and flour two 8x8x2-inch square baking pans; set aside. In a small bowl, combine pumpkin and buttermilk; set aside. In a medium bowl, whisk together flour, cocoa, baking powder, baking soda, and salt; set aside.

In a large mixing bowl, beat butter, granulated sugar, brown sugar, and vanilla together on medium to high speed until light and fluffy. Add eggs, one at a time, beating well after each addition. Alternately add flour mixture and pumpkin mixture, beating on low speed just until combined. Beat on medium to high speed for 20 seconds more. Spread batter into prepared pans.

Bake for 35 to 40 minutes or until a wooden toothpick inserted near center comes out clean. Cool layers in pans on wire racks for 10 minutes. Remove layers from pans. Cool thoroughly on wire racks.

Meanwhile, prepare ganache. In a medium sauscepan, bring 3/4 cup cream just to boiling over medium-high heat. Remove from heat. Add chocolate pieces (do not stir). Let stand for 5 minutes. Stir until smooth. Let stand for 1 to 2 hours or until slightly thickened. Pour the ganache over the cool cake layers. (Place a piece of waxed paper under the wire racks to catch drips.) Let stand for 1 to 2 hours, until ganache sets.

Meanwhile, prepare topping. In a chilled large mixing bowl, beat 2 cups cream, 1/2 cup powdered sugar, the cinnamon and allspice until soft peaks form. Fold in 3/4 cup pumpkin and remaining powdered sugar. Beat on medium speed until stiff peaks form. Chill the topping for 1 hour.

To assemble, place one cake layer on serving platter. If you like, insert four drinking straws to help support the top layer. Snip the straws with scissors about 3/4 inch above the ganache. Spread about 2 cups topping over cake layer. Gently place second cake layer on top. Spoon remaining topping into a pastry bag fitted with a large open star tip. Pipe topping on cake in nine large swirls. Garnish with chocolate curls. Serve immediately; chill leftovers.