Defrost the frozen puff pastry sheets by leaving them out on a countertop for no more than 40 minutes.
In the mean time, wash the spinach and roughly chop it into small pieces.
Chop up the onion and mince the garlic.
Heat up some olive oil in a shallow pan and sauté the onion until translucent.
Add in the garlic along with the oregano and chili flakes and stir for 1-2 minutes on medium/high heat.
Toss in the chopped spinach and stir until it wilts and the excess water evaporates.
Add salt and pepper to taste and then transfer the spinach mixture to a bowl so it can cool down.
Pre-heat your oven to 400° F/ 200° C about 15 minutes before you intend to put in the puffs.
Once the spinach mixture cools completely, add in the crumbled feta and ricotta and stir with a fork until completely incorporated. You can adjust the amounts of cheese that you would like according to your taste.
Taste for seasoning and adjust if necessary. Then set aside.
Whisk the egg in a separate bowl with a tsp of water. This will be the egg wash for the top of the pastry.
Unfold the defrosted puff pastry sheets which will be marked into thirds.
If you plan to use the braided design seen in the image above, make diagonal and equally spaced cuts from the middle all the way along the right and left side of the pastry.
Next, spoon the mixture into the middle section of the pastry and be careful to not overfill.
Next wrap each cut flap across the middle section and alternate between left and right. Do this until the mixture is fully covered by the diagonal flaps.
Brush over the egg wash carefully to ensure the top browns nicely.
Place in the oven and bake for about 30 minutes or until golden brown.
Leave to stand for 10 minutes before serving. Enjoy!
