In a mixing bowl, combine the starter, milk, sugar and egg until well mixed. Add
Add the baking powder, salt, and lemon zest. Mix.
Add the flour and mix until just combined. Add the butter, half at a time, until incorporated throughout. Fold the blueberries into the dough.
Scrape the dough onto a countertop (lightly floured, if needed). Form the dough into a round circle, about an inch thick, about 7 inches in diameter.
Wrap with plastic wrap or beeswax and refrigerate for 30 minutes or up to 3 days for a long ferment.
On baking day, preheat the oven to 425° and remove the dough from the refrigerator, unwrap and place on a parchment lined baking sheet.
Using a knife or bench scraper, slice the circle into 8 wedges. Separate the wedges slightly, giving about 1/2 inch space in between each piece.
Brush each piece with milk and dust with sugar. Place the scones in the upper third of the oven and bake for 18-22 minutes or until golden brown. Cool for 5 minutes before serving.