In a large bowl, with a mixer on medium speed, beat butter and sugar until well blended; add eggs, one at a time, beating well after each addition; beat in vanilla.
Scrape half the mixture into another bowl.
Pumpkin batter: beat pumpkin into half the butter mixture until well blended; in another bowl, stir together 1 3/4 Cup flour, 1 tsp baking powder, 1/2 tsp salt, cinnamon, nutmeg and cloves; add flour mixture to pumpkin mixture and beat on low speed or fold in with a flexible spatula just until blended.
Chocolate batter: in another bowl, mix remaining 1 cup flour, 1 tsp baking powder, 1/2 tsp salt and the cocoa; add flour mixture alternately with buttermilk to the other half of the butter mixture (starting and ending with flour mixture), beating after each addition just until blended.
Spoon half the pumpkin batter into a buttered and floured 12-cup bundt-cake pan; drop half the chocolate batter by spoonfuls over (but not enterly covering) the pumpkin batter; repeat to spoon remaining pumpkin and chocolate batters into pan.
Gently run the blade of a butter knife around the center of the pan several times, then draw the knife across the width of the pan in 10-12 places to swirl batters.
Bake in a 350° oven until a wood skewer inserted into center of cake comes out with a few moist crumbs attached, 55-60 minutes.
Let cake cool 10 minutes in the pan, then invert onto a rack, lift off pan, and cool cake completely before glazing.
Chocolate glaze: in a heat proof bowl or the top of a double boiler, combine semisweet chocolate, whipping cream, butter and corn syrup; Bring an inch or two of water to a boil in a pan that the bowl can nest in, or in the bottom of a double boiler, then remove from heat and place the bowl with the chocolate mixture over the water and let it stand, stirring occasionally, until melted and smooth, about 10 minutes.
Pour warm chocolate glaze over the top of the cake, letting it drip down the sides; sprinkle glaze with peanuts if desired.
Let stand until the glaze is set, about 2 hours, or chill 30 minutes.