Crumble or chop the blue cheese into small pieces. Chop the pears into tiny cubes (if the pears are not ripe enough, add a tablespoon of honey). Mix both ingredients on a bowl.
Spread one of the pastry sheets on a flour-covered surface. Put a tablespoon of filling at regular of the sheet. I made 4 columns by 7 lines, leaving a bit of room between each little mount.
Cover it with the other pastry sheet and adjust the sides so they are right on top of each other. Gently squeeze the top sheet until it reaches the one on the bottom, making marks on the sides of each mount. Make this in all direction until all squares are visible.
Cut each little square with a sharp knife. With a fork, seal the edges.
Spread the pillows on baking trays. I used non-stick trays, but I suppose there’s no need to grease a regular tray, since the pastry is so rich in fat.
Whisk the egg with 1 tablespoon of water. Egg wash each square using a brush.
Take the trays into the oven for about 20 minutes or until the pastry puffs and turns golden.
While the little pillows are still in the oven, wash the arugula leaves and spread some onto several plates (you’re making your appetizer ready). Serve the squares still warm, on top of an arugula bed.