In a small bowl, mix the yeast and brown sugar into the warm water. Let it sit for about 5 minutes, until it starts to foam.

Stir in the salt, pumpkin puree, and pumpkin pie spice. Slowly add half the flour, mixing until combined. Pinch small pieces of the softened butter and add them in, gently mixing.

Add the remaining flour, and once it becomes hard to stir, switch to using your hands to knead the dough until smooth. Knead for about 5-7 minutes, adding flour if needed. The dough should be soft and hold an impression when pressed with your finger.

Place the dough in a lightly oiled bowl, cover with plastic wrap, and let it rise in a warm spot for about 1 hour, or until doubled in size.

Preheat your oven to 450°F. Line two baking sheets with parchment paper.

Once the dough has doubled, punch it down and divide it into 8 equal pieces. Roll each piece into a long rope, about 25 inches, and shape into a pretzel by making a 'U,' crossing the ends, and folding them over.

In a large pot, bring 8 cups of water to a boil. Slowly add the baking soda.

Place each pretzel into the boiling water for 30 seconds, making sure to flip halfway through. Use a slotted spoon to remove and place them back on the baking sheet.

Bake the pretzels for 12-14 minutes, rotating the pans halfway through for even baking. The tops should be golden brown when done.

While the pretzels cool, melt the butter in a small bowl. In another bowl, mix the sugar and pumpkin pie spice.

Once the pretzels are cool enough to handle, brush them with melted butter and coat generously with the pumpkin spice sugar mixture.