Place the liver in a bowl, pour the red wine over it and marinate for at least 1 hour.
Then remove the liver and drain it. Set the red wine marinade aside.
Cut the liver into 1.5 cm cubes and lightly dust them with flour on all sides. Heat 3 tablespoons of oil in a pan and fry the liver on all sides. Remove from pan and set aside on a plate.
Put 3 tablespoons of oil in the pan and fry the shallots until light yellow. Pour in the red wine marinade and the stock, season with salt, pepper and oregano. Let simmer over low heat for about 2 minutes. Add the liver and simmer for 2-3 minutes, stirring, until the sauce thickens. Finely chop the parsley and sprinkle over the finished dish.