Preheat your oven to 400°F (200°C). Line two baking sheets with parchment paper.
In a small bowl, combine the chopped spinach, crumbled feta cheese, dried oregano, and black pepper. Mix gently until the ingredients are evenly distributed.
Lightly flour a clean work surface. Unfold one sheet of the thawed puff pastry. Brush the surface lightly with olive oil.
Spread half of the spinach and feta mixture evenly over the surface of the pastry sheet, leaving a small border around the edges.
Brush the edges of the pastry lightly with the beaten egg wash. Roll the pastry up tightly along the long edge to form a log.
Use a sharp knife to slice the log into 1/2-inch thick rounds (twists). Place the twists cut-side up on the prepared baking sheets.
Repeat steps 3 through 6 with the second sheet of puff pastry and the remaining filling.
Brush the tops of all the crisps with the remaining egg wash.
Bake for 12 to 15 minutes, or until the crisps are puffed, golden brown, and crisp.
Remove from the oven and let cool slightly on the baking sheets before serving. These are best served warm or at room temperature.
Notes
For extra crispiness, you can lightly press down on the twists before baking to flatten them slightly.
If you prefer a different shape, cut the filled pastry into triangles instead of rolling and slicing.
Use high-quality feta cheese for the best flavor in these savory pastry snacks.