Heat the fat in a pot and sauté the frozen onion-garlic mixture in it. Deglaze with broth, add frozen spinach, cover and allow to defrost over medium heat for 16 minutes.
Meanwhile wash the chicken fillets, dab dry and cut in half. Heat the oil in a pan and fry the fillets for about eight minutes, turning them over. Season with salt and pepper and lift them out of the pan.
Deglaze the meat with three tablespoons of water and boil off. Mix sour cream, stock, curry and a little salt. Season spinach with salt, pepper and nutmeg and boil again briefly. Place in a gratin or flat casserole dish and arrange the chicken fillets on top.
Pour the sour cream curry sauce over the fillets and gratinate in the preheated oven (electric cooker: 225°C/ gas: level 4) for 15 minutes. Serve sprinkled with some curry.