Preheat oven to 400°F. Line a baking sheet with parchment paper and lightly grease the parchment with nonstick spray.
Peel the peaches if desired, then thinly slice them.
Gently unroll the puff pastry and cut it into 6 even rectangles.
On the prepared baking sheet, sprinkle a little Demerara sugar in 6 areas, each roughly the size of a puff pastry rectangle. Sprinkle each with cinnamon.
Arrange peach slices over each sugar-and-cinnamon area.
Slice the chilled cream cheese and place a couple of slices over each portion of peaches.
Lay a puff pastry rectangle over each portion and gently press down.
Beat the egg and brush it over the tops of the puff pastry.
Bake until the tops are golden brown, about 20 minutes.