Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a large mixing bowl, whisk together the flour, pumpkin pie spice, baking powder, and salt.

Fold in the chopped walnuts into the dry mixture.

In another bowl, cream together the brown sugar, pumpkin puree, vanilla extract, and eggs until smooth.

Gradually add the dry ingredients to the wet mixture, mixing until a thick dough forms.

Transfer the dough to the baking sheet and shape it into a log about 12 inches long.

Press the remaining walnuts on top and sprinkle with brown sugar.

Bake for 30 minutes, or until edges are golden, then cool for 10 minutes.

Slice the warm loaf into ½-inch thick pieces and lay flat on the baking sheet.

Bake the sliced pieces for an additional 45 minutes, flipping every 15 minutes.

Remove from the oven and let cool completely on a wire rack before storing.