Preheat the oven to 350°F. Butter and flour a 12 cup Bundt cake pan. Tap out the excess flour.
In a bowl, whisk flour, baking powder, baking soda, salt, cinnamon and ground clove. Set aside.
Place chopped chocolate in a microwave safe bowl and microwave for 30 seconds. Stir, and microwave for 10 more seconds. Repeat until all the chocolate is melted. Set aside.
In a large bowl, add melted butter, oil, brown sugar, and granulated sugar and beat on medium for two minutes until well combined.
Add the eggs one at a time, mixing well after each addition (about 30 seconds). Scrape the sides of the bowl to make sure everything is combined. Add vanilla extract and mix. Add pumpkin puree and mix until combined.
Reduce the speed to low, mix in the dry ingredients in 3 parts, alternating with milk. Start and finish with the dry ingredients. Do not overmix.
Add 1 heaping cup of the batter to the melted chocolate and fold it in until mixed.
Alternate adding the chocolate and vanilla batter into the pan. Use a knife or a wooden skewer and swirl the batter slightly.
Bake in the preheated oven for about 45-50 minutes or until a toothpick inserted in the center comes out clean.
Let the cake cool down in the pan for 30 minutes. Then flip it onto a plate or cake stand.