Preheat the oven to 350°F (180°C). Rub butter along the sides and bottom of the loaf pan. Add flour to the pan and rotate it to coat. Line the pan with parchment paper.

Melt the butter in a small saucepan over low heat; then remove from heat and let it cool to about 85°F.

In a medium bowl, whisk together the flour, salt, baking soda, and baking powder for 30 seconds. Add the chocolate chips and toss to coat with the flour mixture.

In a large bowl, combine the granulated sugar, brown sugar, and pumpkin pie spice. Use your fingers to break up any clumps in the brown sugar.

Add the eggs and whisk until combined. Stir in the melted butter until incorporated, then add the pumpkin puree and buttermilk, whisking to combine. Let the batter sit for 10 minutes.

Add half of the flour mixture into the wet ingredients and mix with a silicone spatula until just combined. Fold in the remaining flour mixture until no white bits of flour are visible.

Pour the batter into the loaf pan and smooth the top with an offset spatula.

Bake for 60-70 minutes, or until a skewer inserted into the center comes out clean with a few crumbs. Rotate the pan after the first 30 minutes of baking.

Allow the bread to cool in the loaf pan for 10 minutes before transferring it to a wire rack to cool for 1 hour before slicing.