Preheat oven to 400°. Unfold puff pastry; cut each sheet into 12 sections. Place in greased mini muffin cups, pressing gently onto bottoms and up sides, allowing corners to point up.
In a large bowl, stir together spinach, cream cheese, mozzarella, feta, 1 egg, garlic, pepper and salt. Spoon 1 tablespoon into each cup. Bring pastry corners together and pinch to seal. In a small bowl, beat remaining egg. Brush over pastry edges. Bake until puffed and golden brown, about 20 minutes.