Follow these steps carefully for perfectly flaky and flavourful Spinach Feta Pinwheels:

1. Prepare the Spinach: Ensure your frozen spinach is completely thawed. Place the thawed spinach in a clean kitchen towel or several layers of strong paper towels. Squeeze relentlessly over a sink or bowl until absolutely no more liquid comes out. This step is CRITICAL to avoid a soggy filling and bottom pastry. You should end up with a compact ball of dry spinach. Roughly chop the squeezed spinach to break up any large clumps.
2. Sauté Aromatics: Heat a small skillet over medium heat. Add a teaspoon of olive oil (optional, you can dry sauté if preferred). Add the finely chopped onion and cook for 3-4 minutes until softened and translucent. Add the minced garlic and cook for another minute until fragrant. Be careful not to burn the garlic. Remove from heat and let it cool slightly.
3. Make the Filling: In a medium bowl, combine the softened cream cheese, crumbled feta cheese, the thoroughly squeezed and chopped spinach, the cooled sautéed onion and garlic mixture, about half of the beaten egg (reserve the other half for the egg wash), chopped fresh dill, salt, black pepper, and optional lemon zest or red pepper flakes. Mix everything together thoroughly until well combined and creamy. Taste and adjust seasoning if necessary, remembering the feta adds saltiness.
4. Prepare the Pastry: Lightly flour your work surface. Gently unfold the thawed puff pastry sheet. If it’s too thick, you can lightly roll it out a bit further with a rolling pin to achieve a rectangle roughly 10×12 inches (or follow the natural size of your pastry sheet), ensuring it’s an even thickness. Try to handle the pastry as little as possible to keep it cold.
5. Assemble the Pinwheels: Carefully spread the spinach and feta filling evenly over the puff pastry sheet, leaving about a ½-inch border along one of the longer edges. Don’t spread the filling too thickly, or it will squish out excessively when rolling.
6. Roll the Pastry: Starting from the long edge opposite the clean border, carefully and tightly roll the puff pastry up into a log, like a jelly roll. Try to keep the roll compact to ensure neat pinwheels.
7. Seal the Edge: Lightly brush the clean ½-inch border with a little water or some of the reserved beaten egg. Press gently to seal the log closed.
8. Chill the Log: Wrap the spinach feta log tightly in plastic wrap. Place the log in the refrigerator for at least 30 minutes, or in the freezer for 15-20 minutes. Chilling the log is crucial – it firms up the pastry and filling, making it much easier to slice neat, round pinwheels without squashing them. Do not skip this step!
9. Preheat Oven & Prepare Baking Sheet: While the log is chilling, preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper or a silicone baking mat to prevent sticking and ensure easy cleanup.
10. Slice the Pinwheels: Once chilled and firm, remove the log from the plastic wrap. Using a sharp serrated knife or a very sharp chef’s knife, carefully slice the log into rounds approximately ½-inch thick. You should get about 18-24 pinwheels, depending on the length of your log and thickness of your slices. If the log starts to soften and become difficult to slice, return it to the freezer for a few more minutes.
11. Arrange on Baking Sheet: Place the sliced pinwheels cut-side down on the prepared baking sheet, leaving some space between each one as they will puff up during baking.
12. Apply Egg Wash: In a small bowl, whisk the remaining half of the beaten egg with about a teaspoon of water. Lightly brush the tops and sides of each pinwheel with the egg wash. This gives them a beautiful golden-brown colour and shine once baked.
13. Bake: Place the baking sheet in the preheated oven. Bake for 18-25 minutes, or until the pinwheels are beautifully puffed up, golden brown, and the filling is bubbly. Keep an eye on them towards the end of baking, as oven temperatures can vary.
14. Cool Slightly & Serve: Remove the baking sheet from the oven. Let the Spinach Feta Pinwheels cool on the baking sheet for 5-10 minutes before transferring them to a wire rack or serving platter. They are best served warm but are also delicious at room temperature.