In a bowl, combine the flour, 1/2 cup sugar, baking powder, baking soda and salt. Cut in butter until mixture resembles coarse crumbs. Add sour cream, peaches and vanilla; stir just until moistened.
Turn dough onto a floured surface; knead gently 4-5 times (dough will be sticky). Divide dough in half; gently pat each portion into an 8-in. circle on a baking sheet coated with cooking spray. Cut each into four wedges; separate wedges slightly.
Brush tops with milk; sprinkle with remaining sugar. Bake at 400° for 10-12 minutes or until golden brown.