Wash and dry the spinach, then blanch it for 2-3 minutes in boiling salted water. Drain and blend it.
Prepare a thick béchamel sauce separately. Heat the butter, fry the flour in it and top up with the milk while stirring. Season it to taste with spices. Start adding the yolks one at a time, while stirring nonstop once again. Add the grated feta cheese and blended spinach.
Beat the egg whites separately to snow and mix them carefully with the remaining mixture. Grease baking forms and sprinkle them with some breadcrumbs.
Pour the mixture into them, up to 2/3 of their height. Put them to bake in a heated 392°F (200 °C) oven until they get a nice crust on top.