Preheat oven to 350°F. Lightly grease a baking sheet or use parchment paper.
Spread the nuts out on the cookie sheet and roast for 10 minutes or until browned. Remove and allow to cool.
In a large bowl, whisk together flour, brown sugar, baking powder, salt and pumpkin pie spice; stir well to combine.
In a separate bowl, whisk together pumpkin, eggs, and vanilla, stirring well with a wire whisk.
Slowly stir the wet pumpkin mixture into the dry ingredients. The dough will be very crumbly. Keep working at it, if it needs it add about a tablespoon or less of extra pumpkin puree.
Knead or gently stir the cooled nuts into the pumpkin pie biscotti dough. Place the dough on a lightly floured surface and with floured hands shape into 2 2-inch by 15 inch logs. (I usually just shape mine on the parchment paper.)
Bake for about 25 minutes. Remove from oven and cool for 15 minutes. Reduce oven temperature to 300°F. Cut each log diagonally into 1/2-inch slices using a serrated knife. Place the slices back on the cookie sheets and bake for 15 minutes. Cool completely on wire racks.
If desired, melt white chocolate chips either in a double boiler or in the microwave at 30 second intervals. When smooth, spoon into a condiment bottle and drizzle over the cooled biscotti. Let the chocolate firm up before storing in tins or airtight container.