Tear the cauliflower into florets and cook them for 15-20 minutes in salted water, then mash them. Heat the oil and fry the flour in it. While stirring, add the milk, salt and nutmeg. Stir until thickened.
Mix the puree of cauliflower with white sauce and beaten egg yolks. Season it with salt and dill and add the beaten egg whites. Stir gently, so they don't flatten. Grease a baking pan with butter and sprinkle it with flour.
Add the soufflé and scatter pieces of feta cheese on it. Sprinkle it with breadcrumbs and pieces of butter.
Put the cauliflower soufflé to bake in a preheated 356°F (180 °C) for half an hour to a light tan.