Line a baking sheet with parchment paper and set aside.
In the bowl of a stand mixer fitted with the paddle attachment (or a large bowl with a hand mixer), beat together the softened brown butter, sugar, and brown sugar until smooth.
Add in the egg and vanilla extract and beat until combined. Then beat in the pumpkin puree.
Add in the flour, pumpkin spice, baking powder, and salt and mix until fully incorporated.
Then stir in the chopped pecans if desired. The dough should be sticky.
Scoop half the dough onto one side of baking sheet and pat it into a 10 inch x 2 inch rectangle that’s about 1 inch thick (lightly wetting your hands helps a lot with this step). Repeat with the other half of the dough.
Place the baking sheet with the shaped biscotti logs in the fridge and chill for about 20 minutes (this helps them not spread too much).
While the biscotti logs are chilling, preheat the oven to 350°F.
Bake at 350°F for 20 to 30 minutes, until the top and edges are set. Remove from the oven and let cool for 25 to 30 minutes.
Reduce the oven temperature to 325°F.
Carefully transfer the logs to a cutting board and use a spray bottle filled with room-temperature water to very lightly spritz them (just one spray on each section of the logs). Wait about 5 minutes before using a very sharp serrated knife to slice biscotti ½ inch wide.
Return the pumpkin biscotti slices to the baking sheet, standing them up with ½ inch in between them, so air can circulate around them. Bake for another 25 to 30 minutes, until dry and golden.
Remove from the oven and transfer to a wire rack to cool to room temperature.
Dip the pumpkin biscotti in the melted white chocolate (or drizzle) and sprinkle with chopped pecans.
Let the chocolate fully harden before storing.
Serve the white chocolate pumpkin biscotti with your favorite pumpkin spice latte!
Notes
Store biscotti in an airtight container at room temperature for up to 2 weeks.To freeze biscotti: I recommend freezing the biscotti after the first bake. After the biscotti are sliced, freeze in an airtight container for up to 3 months. To finish baking, let thaw and then bake for 25 minutes as normal.To make brown butter, melt unsalted butter over medium heat, stirring frequently. Watch closely for the butter to develop brown specs and a nutty aroma. Once you start seeing brown specs, let cook for just a few seconds longer (watch very carefully or it will burn). Remove from the heat and pour into a small bowl so that it doesn't continue to cook. Set aside and let cool for about 20 minutes in the fridge until soft and pliable. Note: For every ½ cup (1 stick or 113g), you'll lose about 1 tablespoon (14g) to evaporation while cooking. So you can either add in an extra 1 tablespoon before browning, or if you're browning big batches, just make up the weight difference in your recipe with regular unsalted butter if needed.