Preheat your oven to 400°F (200°C) and prepare a baking sheet lined with parchment paper.

Cut puff pastry sheets into 5-inch squares and keep chilled.

Melt 2 tablespoons of butter in a medium saucepan and add 2 tablespoons of flour; cook until light golden.

Gradually stir in 1 cup of warm milk, whisking continuously until it boils.

Lower heat and let the sauce simmer for about 10 minutes until it thickens.

Add 1 cup of spinach to the béchamel and cook for another minute, followed by 1 cup of chopped ham and half of the grated cheese.

Assemble the puffs by placing béchamel mixture in the center of each pastry square and folding over corners.

Whisk together 1 egg with a splash of cold water for egg wash and coat the tops of puffs.

Bake for approximately 20 minutes, or until the puffs are golden brown.

Allow to cool slightly before serving.