Lancashire lunch in one dish

Cut the lamb into small pieces, cut excess fat. Cut the kidneys lengthwise, cut out the ducts, rinse thoroughly. Peel and roughly chop the potatoes. Rinse the mushrooms well, cut in half without peeling. Peel and finely chop the bulb onions. Put all the ingredients in layers in a clay pot, the last layer is potatoes. Salt and pepper each layer. Pour all over the stock and melted butter, cover and simmer for 3 hours over low heat, shaking the pot occasionally.