Preheat the oven to 425°F (220°C) and line a 12-cup muffin pan with paper liners.

In a small saucepan, melt the butter over low heat and let it cool to about 85°F.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt for about 30 seconds. Toss in the chocolate chips to coat.

In a separate bowl, combine the brown sugar, granulated sugar, and pumpkin pie spice. Break any clumps of brown sugar.

Add the eggs to the sugar mixture and whisk until lightened in color. Pour in the cooled melted butter, then add buttermilk and pumpkin puree, mixing well and letting it sit for 10 minutes.

Fold half of the dry mixture into the wet ingredients, then add the remaining dry ingredients until no obvious flour remains (batter will be lumpy).

Divide the batter among the muffin cups, filling each to the top.

Bake in the oven for 5 minutes, then reduce temperature to 350°F (175°C) and bake for an additional 15-18 minutes.

Check doneness with a toothpick; it should come out with a few crumbs. Internal temperature should reach about 202°F.

Let the muffins cool in the pan for 5 minutes before transferring to a wire rack.