If the spinach is raw, saute and chop. Do not add water. If frozen, defrost.
Grate the cheeses and beat and add egg. Add Spinach and mix. Add salt and peper to taste.
Melt a decent amouont of butter. Paint the inside of a rectangular dish. Place filo sheet in the dish, It will overlap the sides - don't worry. Add paint with some butter and add the next sheet and the next. Put the mixture in the dish on top of the filo. Add the next three sheets. Roll and fold in the edges so that they form a kind of crust. Place in an over on around 170. Middle shelf - until brown.