Finely dice the onions. Mix the minced meat with the egg, mustard, tomato paste and 2 onions. Season to taste with oregano, gyros spice, salt and pepper. Shape the minced dough into 4 oval loaves of the same size. Press in a piece of feta cheese at a time and enclose it with the mince.
Heat the clarified butter in a pan. Fry the Bifteki on all sides for about 5 minutes. Take out and put in a baking dish.
Sweat the remaining onion cubes, stir in 75 ml of water, Metaxa and cream, bring to the boil, season with broth to taste. If necessary thicken with sauce thickener.
Pour the sauce over the bifteki. Sprinkle with the crumbled feta cheese and bake for about 15 minutes at 200 ° C.