Step 1

Pre-heat your oven to 400°F.

Step 2

Cut the puff pastry sheets into 5-inch (13cm) squares. Set aside in the refrigerator.

Step 3

Melt butter over medium heat in a saucepan. Add flour and salt; cook for 1 minute, stirring frequently.

Step 4

Pour in the warm milk in 2 batches, whisking constantly until smooth and boiling.

Step 5

Reduce heat to low and simmer, stirring occasionally until sauce starts to thicken.

Step 6

Add in spinach and cook for 1 minute, just until wilted.

Step 7

Add ham and 1 cup of Swiss cheese and stir well. Set aside.

Step 8

Arrange the puff pastry squares on a parchment-lined baking sheet.

Step 9

Top with a heaping spoonful of ham and cheese mixture, and sprinkle with grated cheese.

Step 10

Fold the corners onto the top, forming a smaller square.

Step 11

Brush the pastry with the egg wash, making sure to coat all sides.

Step 12

Bake for 20 minutes, until puffed and golden.