Start with preparing the kidney. Cut away white and spongy interior parts and sprinkle the kidney with salt and leave it for about 1 hour. Rinse under cold running water and leave it for another hour in a bowl with 1 litre of cold water and 1 dl of white wine vinegar. In this way, the kidney will bleed but it is necessary to avoid the very intense taste.
Drain the kidney, rinse again and dry with a kitchen paper. Cut it into pieces and then into thin slices of 3-4 mm. Heat 2 tablespoons of oil and 20 g of butter with the clove of garlic peeled and crushed into the Pan, preferably nonstick. When the fat will sizzle, add the kidney slices and brown over a lively flame for 3-4 minutes.
Sprinkle the sliced kidney with 2 tablespoons of Balsamic Vinegar of Modena IGP and allow it to evaporate completely then add salt and pepper. Turn off the flame and add 30 g of soft butter. Mix it, close the lid and leave it for 1 minute. Sprinkle with chopped parsley and serve.