Let the pears simmer, uncovered, until they start to break down, about 15 minutes, stirring a few times. Remove from the heat. Remove and compost the vanilla bean. Using a potato masher, coarsely crush the pears.
Transfer the mixture into a bowl and let cool. Cover and refrigerate for 1 hour.
Assembly
Line a baking sheet with a silicone mat or parchment paper.
On a floured work surface, roll out the shortcrust pastry to form a 15 x 10-inch (38 x 25 cm) rectangle. Using a 5-inch (12.5 cm) round cookie cutter or bowl, cut out 6 circles of dough. Roll the centre of the circles to form into ovals 8 inches (20 cm) long, leaving a ½-inch (1 cm) boarder at the top and bottom of the ovals, so that the edges of the dough are thicker than at the centre.
Place about 3 tbsp (45 ml) of the pear filling over the top half of each oval of dough. Using a pastry brush, cover half of the boarder of dough with water. Fold the dough in half over the filling. Press around the filling with your fingertips to seal the dough. Finish sealing the dough by pressing two fingertips around the entire edge of the turnovers, then pressing the back of a knife in between the finger imprints.
Place the turnovers on a baking sheet. Freeze for 30 minutes.
With the rack in the middle position, preheat the oven to 400°F (200°C).
Flip the turnovers over so that the flat side is facing up. Using a pastry brush, cover the turnovers with the egg yolk. Using a knife, score the dough (without going all the way through) into decorative leaf patterns. Make an incision at the bottom of the turnover to allow the steam to escape while baking.
Bake for 25 to 30 minutes or until the turnovers are dark brown. Once out of the oven, immediately brush the turnovers with the maple syrup. Let cool before serving. The turnovers will keep for 3 days in an airtight container at room temperature.
