Wash the spinach and put it in hot water for 5-6 min. Once it cools a bit, cut it into strips but save the water.
Braise the finely chopped onions in a pan with 2 tbsp oil and the butter. Add the flour and once it reddens a bit, pour in 2 cups of the broth from the spinach.
Stir until thickened and add the beaten eggs, feta cheese and black pepper.
Continue sauteing for 2-3 min., while stirring nonstop until the eggs become thread-like.
Serve the porridge warm with a little extra crumbled feta in the middle of the plate.