Preheat your oven to 400°F (200°C).
Thaw the puff pastry sheets according to package instructions.
In a mixing bowl, combine diced ham, chopped spinach, and shredded cheese.
Season the mixture with salt, pepper, and garlic powder (if using).
Roll out the puff pastry on a floured surface and cut into squares (about 4x4 inches).
Place a spoonful of the filling in the center of each square.
Fold the pastry over to create a triangle and press the edges to seal.
Brush the tops of the puffs with the beaten egg.
Arrange the puffs on a baking sheet lined with parchment paper.
Bake in the preheated oven for 15-20 minutes or until golden.
Remove from oven and allow to cool slightly before serving.