Start by chopping the spinach finely so it blends well with the cheeses. In a bowl, combine the spinach, crumbled feta, softened cream cheese, minced garlic, black pepper, and oregano. Mix everything until you get a creamy, evenly combined filling. This mixture will hold together nicely when baked inside the pastry.
Lightly flour your work surface and roll out the puff pastry into a rectangle about 10×12 inches. If your pastry sheet already comes in this size, just smooth it out. Cut the sheet into two even rectangles, as you’ll be layering them with the filling in between.
Spread the spinach and feta filling evenly over one of the pastry rectangles. Make sure to spread it all the way to the edges so each twist has plenty of flavor. Place the second pastry sheet on top and press lightly to seal the layers without flattening too much.
Using a sharp knife or a pizza cutter, slice the layered pastry into strips about 1 inch wide. Take each strip and gently twist it a few times to form spirals. Arrange them carefully on a baking sheet lined with parchment paper, leaving space between each one as they will puff up.
Brush each twist with the beaten egg using a pastry brush. This gives the pastry a glossy golden finish. For extra crunch and flavor, sprinkle sesame seeds or poppy seeds on top. Bake in a preheated oven at 400°F (200°C) for about 18–22 minutes, or until the twists are puffed and golden brown.
Remove from the oven and let the twists cool for a few minutes. This makes them easier to handle and enjoy. Serve them warm for the best flavor, but they also taste great at room temperature. Perfect on their own or with your favorite dipping sauce.