Place the finely chopped spinach in a bowl with the onion, the spearmint, the fennel, the mizithra or anthotyro (whichever of the two you prefer, or both), salt, pepper and a bit of oil and combine to an even mix. Fill a plate with the mix that you have prepared and start.
Make the dough with the flour, the oil and the salt. Roll out the dough to a sheet that is not very thin.
Cut out with a knife into squares and fill each one with a tablespoon of the filling that you already have on your plate.
Fold the two opposite corners of the pastry.
Do the same with the two remaining corners and press at the center of the kalitsouni lightly with your fingers to seal.
Spread them out on a baking tray lined with baking paper, brush them with the beaten egg and sprinkle sesame over them.
Bake in a preheated oven at 180-200°C for about 1 hour. Bon appétit!!
