Preheat oven to 400 F (200 C). Line baking sheet with parchment paper.
In a large bowl, combine flour, sugar, baking powder, salt, and rosemary.
Chop chilled butter into small cubes. Cut butter into dry ingredients using a fork (or two!) or a pastry blender / cutter until mixture is distributed throughout, and mixture resembles gravel.
Add peaches, milk, and balsamic vinegar to dry ingredients, stir JUST until combined - mixture will be a little sticky.
Turn dough out onto a floured surface, sprinkling some flour on top. Gently knead for a few seconds, then gather dough up into a ball.
Press down to a disk that’s an even 1" thickness, cut into 6 wedges.
Transfer scones to prepared baking sheet, brush with the remaining milk.
Bake for about 25 minutes or until golden brown.