Position an oven rack in the middle of the oven and preheat the oven to 400 degrees F. Grease a muffin pan.

In a large bowl, whisk together the all-purpose flour, whole wheat flour, baking powder, pumpkin pie spice, salt and baking soda.

In a second bowl, whisk together the brown sugar, eggs, oil, pumpkin puree, buttermilk and vanilla until well blended.

Add the egg mixture to the flour mixture and stir just until blended and then gently stir in the chocolate chips.

Divide the batter equally among the cups of the prepared muffin pan.

Bake in the preheated oven until the tops are golden and a toothpick inserted in the center of the muffins comes out clean, about 17 to 21 minutes.

Remove from the oven and let the muffins cool in their pan on a wire rack for about 5 minutes, then remove them from the pan and place them on the wire rack to cool.