Place a rack in the center of the oven and preheat to 180C.
In a large mixing bowl, sift together flour, sugar, baking powder and salt. Cut the butter in small cubes and then slowly rub it into the flour mixture till until it resembles coarse meal or bread crumbs.
In another bowl combine egg, 3/4 cup of buttermilk and vanilla, and beat lightly. Add the liquid to flour mixture and combine to make a soft dough. Do not over knead. Chill the mixture for 10 minutes.
Take the dough out from the refrigerator and gently roll the dough into an even round of about 1/2 inch thickness. Dust with flour if the dough is sticking to the surface or the rolling pin. You can always use a pastry brush to remove extra dry flour.
Brush half of the rolled out dough with buttermilk (the leftover 1/4 cup). Arrange peach slices, in a single layer, across the buttermilk moistened dough. Sprinkle with half of the cinnamon sugar mixture. Carefully pick the empty side of dough and fold over the peach sliced layer. Press the edges of the dough to seal the ends. Using a floured knife or a pizza cutter, slice dough into even pieces (about 8-10).
Place the scones on lined baking sheets or silpat, leaving enough room for them to expand. Brush each scone top with buttermilk, and sprinkle with remaining cinnamon sugar.
Bake for 15-18 minutes, until golden brown and cooked through.