Remove dough from the refrigerator. Place on a floured piece of parchment measuring 12" long and wide. I transfer the dough and paper to a rimless baking sheet.
Beat your ball of chilled dough with a rolling pin and knead the dough briefly around the edges to soften slightly. Moving from below center, roll the dough out to the edge. Lift the dough, turn it slightly, and give another roll. Sprinkle dough on the top and bottom with flour and keep rolling.
Create an 11" circle with the dough. I needed the edges a bit thicker to lift it over the top of the galette.
Starting 1 to 1½ inches from the edge of the round, arrange the peach wedges in a single layer in concentric circles until you reach the center of the circle. When placing the peaches on the dough, leave the extra juice in the bowl and not on your galette.
Fold the outer edges of the pastry over the peaches, creating overlapping folds as you work around the perimeter. Once you form the galette, ensure no cracks in the dough where the peach filling can seep.
Brush the top of the pastry with the beaten egg and sprinkle with sugar.
If your galette is juicy, place another baking sheet underneath to catch any juices overflowing.
Bake for 50 to 60 minutes, until the crust is golden and the filling is cooked.
Let the galette cool on the baking sheet on a wire rack. Cut into wedges and serve warm.