Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.

In a skillet, heat the olive oil over medium heat. Add the minced garlic and sauté for 30 seconds until fragrant.

Add the chopped spinach to the skillet and cook for 2-3 minutes, stirring occasionally, until wilted. Season with salt and black pepper, then remove from heat and let it cool slightly.

In a mixing bowl, combine the cooked spinach, crumbled feta cheese, and grated Parmesan cheese. Mix well.

Roll out the thawed puff pastry sheet on a lightly floured surface. Spread the spinach and cheese mixture evenly over the pastry, leaving a small border around the edges.

Starting from one edge, tightly roll the pastry into a log. Seal the edge with a bit of water to keep it from unraveling.

Using a sharp knife, slice the log into 1/2-inch thick pinwheels and place them cut-side up on the prepared baking sheet, leaving space between each piece.

Brush the tops of the pinwheels with the beaten egg for a golden finish.

Bake in the preheated oven for 15-18 minutes, or until the pinwheels are puffed and golden brown.

Remove from the oven and let them cool slightly before serving.