1. Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper to prevent sticking.
2. Heat olive oil in a small pan over medium heat. Add minced garlic and sauté for about 30 seconds until fragrant.
3. Toss in the chopped spinach and cook until wilted, about 2-3 minutes. Remove from heat and let cool slightly.
4. In a mixing bowl, combine the cooked spinach, crumbled feta, mozzarella (if using), salt, pepper, and dried oregano. Stir gently to mix.
5. Unfold your thawed puff pastry sheet on a lightly floured surface. Cut the sheet into 4 equal squares.
6. Spoon a generous tablespoon of the spinach and feta mixture onto the center of each square.
7. Fold each square into a triangle by bringing one corner over the filling to the opposite corner. Press edges firmly to seal—use a fork to crimp the edges if you like.
8. Place the prepared croissants on the baking sheet, spaced evenly apart.
9. Brush the tops with the beaten egg to give them that beautiful golden shine.
10. Bake for 15-18 minutes, or until the croissants are puffed and golden brown.
11. Remove from oven and let cool for 5 minutes before serving.

Here’s a little secret from my kitchen: if you’re pressed for time, you can prepare the filling in the morning or even the night before. Just keep it covered in the fridge, and you’ll have a quick assembly meal ready when hunger strikes. Life with kids and work taught me that a little prep goes a long way.