- Preheat oven to 200°C (400°F).
- Cut each sheet of puff pastry into 6 squares measuring about 8 cm x 8 cm (3 in. x 3 in.).
- Heat oil in a skillet over medium-high heat and wilt spinach. Set aside.
- Spoon about 60 mL (¼ cup) bechamel sauce, reserved spinach, and swiss cheese onto each pastry square.
- Fold corners into the middle of each square and seal well.
- Beat egg yolk with water and brush onto dough. Season with freshly ground pepper.
- Bake in the oven for 25 to 30 minutes, until pastry is flaky and golden.
Perfect for finishing off leftover chicken bechamel sauce, this recipe makes a good brunch dish.