01 - Preheat the oven to 400°F. Line a baking tray with parchment paper.
02 - In a mixing bowl, combine spinach, feta cheese, cream cheese, garlic, half the beaten egg, dill, black pepper, and salt if using. Mix thoroughly until uniformly blended.
03 - Unroll the puff pastry sheet on a lightly floured surface. Spread the spinach and feta filling evenly over the pastry, leaving a ½-inch border along one long edge.
04 - Starting from the opposite long edge, tightly roll the pastry into a log. Seal the edge with a small amount of water.
05 - Using a sharp knife, slice the log into ¾-inch thick pinwheels (approximately 20 pieces). Place them flat, cut side up, on the prepared baking tray.
06 - Brush the tops of the pinwheels with the remaining beaten egg.
07 - Bake for 18 to 20 minutes or until puffed and golden brown.
08 - Let cool slightly before serving warm or at room temperature.