Method Blanch the onions and drain. Skin the kidneys, cut in half lengthways and core.
Heat a saute or deep frying pan, drop in the butter and, when it is foaming, put in the kidneys and saute briskly until evenly browned.
Lift out kidneys and put in chipolata sausages, lower the heat and cook until brown on all sides. Take them out, add the onions and mushrooms, shake over a brisk heat for 2-3 minutes, then draw pan aside.