Preheat the oven to 350°F (180°C) and line a baking sheet with parchment paper.
Cut each puff pastry sheets into 4-6 equal squares and transfer to the baking sheet.
Score a ⅔ inch / 1.5cm border around each square but don't cut completely through the puff pastry.
Peel the pear, cut it into quarters, remove the core and chop the quarters into little cubes.
Divide the pear cubes, crumbled blue cheese (I use gorgonzola) and chopped walnuts between the puff pastry squares, staying within the border.
Brush the border of the pastries with egg wash and bake for 20 to 25 minutes, until golden brown and the cheese is melted.
Remove the tarts from the oven and let them cool for 5 minutes. Top with a little bit of lingonberry jam before serving.