How to Make It
In a medium nonreactive saucepan, combine the pears and pear juice and bring to a simmer over moderate heat. Cook, stirring occasionally, until the pears are tender when pierced, about 30 minutes. Drain the pears (you can save the juice to drink) and refrigerate them until cool, about 1 hour or overnight.
Preheat the oven to 425°; line a baking sheet with parchment paper.
Pour the sugar into a medium bowl. using the back of a table knife, scrape the seeds from the vanilla bean and mix them into the sugar. Chop 1 of the cooled pears into a chunky paste and toss with 1 tablespoon of the vanilla sugar.
On a lightly floured work surface, roll the puff pastry dough into a 10-inch square. Cut the dough into four 5-inch squares. Slightly round off 2 corners or each square to resemble bread slices. Transfer the "toasts" to the prepared baking sheet and refrigerate until chilled, about 10 minutes. Divide the pear paste among the toasts and spread almost to the edges. Cut the remaining pears crosswise into 1/8-inch slices and arrange them, overlapping, on the toasts and sprinkle evenly with the remaining vanilla sugar.
Bake for about 15 minutes, or until golden brown on the bottom and edges. Remove the toasts immediately to a rack and let cool before serving.