Preheat the oven to 400°F (200°C).
Roll out the puff pastry just enough to fit the bottom of a 10-inch oven-safe skillet. Press it gently into the base and slightly up the sides. Refrigerate while you prepare the filling.
In a small bowl, mix together the cinnamon, brown sugar, and cornstarch.
Sprinkle half of the cinnamon-sugar mixture evenly on the bottom of the puff pastry.
Arrange the peach slices over the spiced base in overlapping circles or rows.
Sprinkle the remaining cinnamon mixture evenly over the peaches.
Fold the edges of the puff pastry slightly over the filling to create a rustic border.
Brush the crust with egg wash and sprinkle with coarse sugar.
Drizzle the melted butter over the peach filling.
Bake in the oven for 30-35 minutes, or until the crust is golden and the peaches are bubbling.
Let cool for 10–15 minutes before slicing. Serve warm with ice cream or whipped cream.
