Preheat oven to 350°F
In a large bowl, mix all-purpose flour, pumpkin spice, baking powder, and salt. Set aside
Add all the sugar and butter to a large bowl or a standing mixer. Use a hand mixer or a standing mixer to cream the softened butter and sugar until light and fluffy. Next, mix in eggs one at a time. Once the eggs are fully incorporated, mix in the pumpkin and vanilla extract.
Gradually add the dry ingredients to the wet mixture, and continue mixing until a dough forms. Turn off the mixer and add the dates and pecans. Gently mix them into the dough.
Turn the dough out onto a lightly floured surface and roll it into a ball. Divide the dough ball in half. Roll each half into a 12-inch-long log.
Transfer both logs to a large parchment or silicon-lined baking sheet. Flatten each log so that it's 12 inches long, 3 inches wide, and ¾ inch high.
Bake for 25 minutes on the middle rack, then let cool slightly. Use a sharp knife to slice the logs into 1-inch-wide pieces.
Turn each piece on its side and bake for another 15 minutes.
In a small bowl, mix all of the Pumpkin Icing Ingredients and set aside.
Once the biscotti have cooled, drizzle pumpkin icing over the biscotti.