Preparation

1. Preheat the oven to 400 F. Line a large sheet pan with parchment paper.
2. Unwrap the puff pastry and place on a lightly floured counter. Use a rolling pin to roll lightly, just to smooth the dough. Transfer the dough to the baking sheet.
3. Use a pastry brush to brush the pastry all over with egg white. Reserve remaining egg white.
4. In one small bowl, mix two tablespoons of the sugar with the all-purpose flour. Sprinkle over the egg wash, leaving a ½-inch rim bare.
5. Mix the remaining sugar in the same bowl with the crystallized ginger and lemon zest and reserve.
6. Slice each pear in half vertically, then use your paring knife to slice out the stem and seeds, keeping the half intact. Place on the cutting board, cut side down, and cut the pear into thin slices, keeping the pear in place so it stays in the same shape. Repeat with all the pears.
7. Make three rows of pear slices, running lengthwise, fanning each slice to cover the crust evenly.
8. Fold the edges of the puff pastry in to form a rim, and crimp with a fork. Brush the rim with remaining egg white. Sprinkle the pears with the ginger mixture.
9. Bake on the lower shelf in the oven for 20 minutes, until puffed and golden. Let cool on a rack for five minutes before cutting.