Preheat oven to 425℉. Line a large baking sheet with parchment paper. Set aside.

In a large mixing bowl, whisk together the flour, sugar, baking soda, baking powder, and salt.

Use a cheese grater to grate the cold butter into shreds quickly.

Mix the butter shreds into the flour mixture until well coated and crumbly.

Stir in the chopped pecans.

In a separate medium bowl, stir together the sourdough starter, milk, and maple syrup.

Pour the wet ingredients over the dry ingredients and gently stir until a shaggy dough forms; do not overwork the dough.

Transfer the dough to a lightly floured surface and shape it into a 9-inch circle.

Cut the dough into 8 equal wedges with a large knife or bench scraper.

Place the wedges on the prepared baking sheet, spacing them at least 1½ inches apart.

Bake the scones for 5 minutes at 425℉. Then, reduce the heat to 375℉ and continue baking for another 10 minutes. Allow to cool before glazing.

To make the glaze, combine melted butter, maple syrup, milk, and powdered sugar in a small bowl; mix until smooth.