Preheat the oven to 350 degrees F and line a baking sheet with parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment, add the unsalted butter, granulated sugar, pumpkin pie spice, cinnamon, baking powder, and salt and beat until fully combined.
Beat in the pumpkin purée and egg.
Then, mix the flour in until just combined.
Turn the dough out onto the prepared baking sheet and shape into a 10x3 inch loaf. Use a rubber spatula dipped in water to easily smooth out the top.
Bake the biscotti dough for 25 minutes.
Allow the biscotti to cool for 5 minutes, then cut 1 inch pieces diagonally with a cerated knife.
Turn the oven down to 325 degrees F and bake the biscotti for another 35 minutes, flipping them over half way through.
After 35 minutes, turn the oven off, crack the door open, and allow the biscotti to cool completely in the oven.
For Dipping in Chocolate:
Melt the chocolate and oil together in the microwave in 20 second intervals until fully melted and smooth.
Once the biscotti are completely cooled, dip each of them in chocolate and top with flaky sea salt, if desired.