1. Poach the pears: Combine white wine, lemon juice and peel, granulated sugar, cinnamon sticks, and vanilla bean and seeds in medium saucepan over high heat. Bring to a boil and cook for 5 minutes. Add the pears, lowering the heat, and cook for 20 to 30 minutes, until pears are tender. If necessary, turn the pears very gently by rotating the stems with your fingertips so that they cook evenly. Remove the pears to a bowl, bring the poaching liquid to rapid boil, and reduce by half. Pour the syrup over the pears and refrigerate, covered, for at least 6 hours, preferably overnight.

2. Assemble the dumplings: Roll out the pastry to a thickness of no more than 1/8 inch. Using a sharp paring knife or pastry wheel, cut dough into triangles (using the pear as a guide for the size). Cut as many leaf shapes as possible from the pastry scraps, and use the back of a paring knife to make the vein markings. Keep the pastry chilled on parchment-lined baking sheets until ready to use.

3. Preheat oven to 400 degrees. Mix the sugar and cinnamon in a small bowl; set aside. Remove pears from poaching syrup and pat dry. Reduce syrup to about a cup for serving. Using a Parisian scoop, core each piece of fruit carefully, starting from the bottom to within 3/4 inch of the top; take care to leave the stem intact. Fill each fruit with some of the cinnamon-sugar mixture and dot with butter. Invert each pear onto the center of the triangle of pastry. Lightly brush edges of dough with egg wash. Bring the edges of the pastry together and pinch to seal. Garnish the dumplings as desired by pasting the leaves on with egg wash. Lightly brush each dumpling with egg wash and, if desired, sprinkle with sanding sugar. Place the dumplings on a parchment-lined baking sheet and chill until ready to bake.

4. Cover stems with a small piece of parchment-lined foil. Bake in upper third of oven for 30 to 35 minutes. Transfer to wire rack and cool slightly, about 15 to 20 minutes. Spoon a couple of tablespoons of reduced syrup around the base of each pear. Serve warm.