Slice pears into 1/8” thick pieces longitudinally (leave the peel on). Mince 2 sage leaves.
Toss pears with minced sage, lemon juice, brown sugar, and flour. Set aside.
Preheat oven to 350F.
Role pastry between two sheets of lightly floured parchment into a 14-16” circle ¼” thick. Use a plate to trace a perfect circle or leave edges for a rustic look. Remove top layer of parchment. Place rolled pastry on a baking sheet – leaving the bottom layer of parchment as it is. It is ok if the edges of the pastry are over the side of the sheet at this point.
Heap or carefully arrange pear mix into center 10” 0r 11” of pastry. Flatten to about the same thickness throughout. Using the parchment to help lift, fold the edges of the pastry over the pears to form 6 sides (pulling the parchment back flat after). Press of the areas of overlap to adhere them together.
Skip this step if making vegan. Whisk egg white with water. Brush onto all exposed pastry lightly. Sprinkle a fine layer of granulated sugar on top.**
Bake for 40-50 minutes, until pastry is golden-brown and filling is bubbling. Allow to cool for at least 20 minutes before serving. Excellent with a dollop of crème fraiche or whipped cream.