Liuzhou, You will need to clean the kidneys and soak them in salted water for around 30 min (you may add a slice of ginger). After that pat dry and fry over high heat in clarified butter with garlic and persil for about two minutes. Alternatively, with ginger and finely sliced scallions in neutral oil and add a tiny bit of Zhenjiang vinegar at the end. Anything longer than two minutes will result in a rather "al dente" experience ...