2/3 cup vegetable oil
1-1/2 cups semisweet or dark chocolate chips
3/4 cup granulated sugar
1/2 cup light brown sugar
4 large eggs
1/2 teaspoon vanilla extract
1 cup pumpkin puree
1-3/4 cups flour
1 teaspoon ground cinnamon
1 teaspoon baking soda
1/2 teaspoon baking powder
1/2 teaspoon salt
1/4 teaspoon ground ginger
1/4 teaspoon ground allspice
1/4 teaspoon ground cloves
Preheat the oven to 350 degrees with the rack in the middle. Grease a 9-by-5-inch loaf pan with vegetable oil.
Chop 1/3 of the chocolate chips into small bits; return them to the remaining chocolate.
With hand mixer or stand mixer fitted with a flat beater attachment, combine the granulated and brown sugars, eggs and vanilla. Mix on low speed until smooth, about 1 minute.
Add the pumpkin puree and 2/3 cup oil and mix on low until thoroughly combined, about 1 minute.
In a medium bowl, whisk together the flour, cinnamon, baking soda, baking powder, salt, ginger, allspice and cloves until combined.
Add the dry ingredients to the pumpkin mixture and mix on medium-low speed until just incorporated and no bits of flour mixture remain. Fold in the chocolate chips.
Pour the batter into the loaf pan and smooth out the top. Sprinkle extra brown sugar and cinnamon on top, if desired.
Bake for about 1 hour and 20 minutes, or until the top of the bread is firm to the touch and springs back when lightly pressed with your finger, and a cake tester or wooden pick produces only chocolate when inserted into the bread.
Transfer the loaf pan to a wire rack and let cool completely. To unmold, run a knife around the perimeter of the loaf pan and invert the pan. Slice the bread and serve at room temperature.