Soak the kidney in warm salted water for 30 mins. Wash the mushrooms, peel and cut into pieces, chop the stalks finely. Cut the kidney into small pieces, removing the hard core and fat. Peel and chop the onion. Heat the fat in a big saucepan and fry the onion and kidney and mushrooms for five mins, turning to cook evenly. Push to one side and stir in the flour and seasonings, then stir in half the stock and stir until it boils.
Cover and simmer gently for 3/4 hour, then add the well washed rice and remainder of stock. Continue to simmer gently for 12-15 mins more or until rice is tender. Skim if necessary and serve.
Taken from: Early Settlers Household Lore. Sovereign Hill Ballarat.