Preheat the oven to 350ºF degrees. Line a large baking sheet with parchment paper or a silicone baking mat. Lightly flour the baking sheet. Set aside.
In a medium size bowl, whisk together the butter, pumpkin, egg, and sugar until combined. Set aside.
In a large bowl, toss together the flour, baking powder, spices, and salt. Add the wet ingredients to the dry ingredients and gently mix with a large wooden spoon or sturdy rubber spatula until everything is combined.
Check out this Instagram reel to see how I make my biscotti. Turn dough out onto lightly floured baking sheet and, with floured hands, pat dough into a rectangle about 1/2" thick. My rectangle was 6" wide and 7 and 1/2" long (using a ruler or a ruled silicone baking mat is helpful here). Sprinkle with prepared sugar/spice coating.
Bake dough slab for 20-22 minutes, or until the top and sides of the slab are lightly browned. Remove from the oven, but do not turn off the heat. Place baking sheet on a wire rack and allow to cool for 10 minutes.
Once the dough is cool enough to touch, cut into 1" thick slices using a sharp knife. Cut these 1" slices in half, making a perpendicular slice down the entire slab. Set slices cut sides up on the baking sheet.
Return to the oven to bake for 6 minutes. Remove from oven, turn biscotti over, and bake the other side for 6 minutes. Remove from the oven and allow to cool for 3 minutes on the baking sheet (cookies will become crunchy as they cool). Transfer biscotti to a wire rack to cool completely. Cookies stay fresh covered tightly at room temperature up to 7 days. Cookies freeze well, up to 2 months. Thaw at room temperature.