Preheat the oven to 350 degrees F, line a large cookie sheet with parchment paper, set aside.
In a large mixing bowl combine the sugar, eggs, oil, vanilla extract, and pumpkin puree, whisk well to combine. In a small mixing bowl combine the flour, baking powder, spices, and salt, mix to combine.
Fold the dry ingredient's into the wet ingredients until thoroughly mixed. Scoop the batter onto the prepared cookie sheet, keeping it in a sort of loaf shape, the batter will be sticky. Spray your hands with non-stick spray or run the under some cold water, using your hands form the cookie dough into a long rectangle, about an inch thick.
Bake at 350 for 30-35 minutes until the biscotti is soft, but sliceable. Remove from the oven and allow to cool slightly - about 5 minutes. Using a serrated knife slice into even slices, about 1 inch wide. Lay the biscotti slices out in a single layer on the cookie sheet and return to the oven to bake for 7 more minutes, flip the biscotti and return to the oven once more for 7 more minutes.
Once done, transfer to a cooling rack. Melt the chocolate chunks until smooth and dip each biscotti slice, transfer back onto the cooling rack so any excess chocolate can drip off. Allow to cool completely, transfer to an airtight container and keep up to a week.