Preheat oven to 425°F. Line a large baking sheet with parchment paper or a silicone baking mat.
Whisk 1 cup all-purpose flour, 1 cup whole-wheat flour, 3 tablespoons brown sugar, 2 teaspoons baking powder, 1 teaspoon pumpkin pie spice, ½ teaspoon kosher salt and ¼ teaspoon baking soda together in a large bowl.
Combine 1 cup pumpkin puree and ½ cup buttermilk (or yogurt) in a measuring cup; whisk well.
Add cubed cold butter to the flour mixture. Using your fingers or a pastry cutter, work the butter into the dry ingredients until the mixture resembles coarse meal. Add the pumpkin mixture and stir until just combined. Fold in ¼ cup chocolate chips.
Scoop the dough into ⅓-cup mounds on the prepared baking sheet, spacing them 2 to 3 inches apart. Bake until the bottoms are golden, 15 to 20 minutes. Let cool on the pan for at least 10 minutes before glazing.
Make glaze (if using): Whisk ½ cup confectioners’ sugar, 1 tablespoon milk and ¼ teaspoon pumpkin pie spice (if using) in a small bowl until smooth. Drizzle over the cooled scones, if desired. Serve warm or at room temperature.
