Steps
1. Preheat your oven to 200°C (400°F).
2. Heat olive oil in a pan over medium heat. Add the chopped onion and garlic, sauté until translucent.
3. Add the chopped spinach to the pan and cook until wilted. Remove from heat and let cool.
4. In a bowl, combine the cooked spinach mixture with crumbled feta, salt, and pepper.
5. Roll out the puff pastry sheet on a floured surface and cut into 4 equal squares.
6. Place a spoonful of the spinach and feta filling in the center of each square.
7. Fold each square into a triangle or rectangle, sealing the edges by pressing with a fork.
8. Brush the tops with egg yolk and sprinkle with sesame seeds if using.
9. Place bourekas on a baking sheet lined with parchment paper.
10. Bake for 20-25 minutes or until golden brown and puffed.
11. Remove from oven and let cool slightly before serving.