To make the filling, heat a non-stick frying pan over a high heat. Add the beef and fry, stirring occasionally, for 4 minutes until browned on all sides. Transfer to a bowl, add the kidney and set aside.
Heat the oil in the pan, then add the leeks. Stir, then cover and cook gently for 4 minutes until starting to soften. Stir in the rutabaga and carrots, cover and cook for a further 4 minutes until lightly browned. Add the beef and kidney; season to taste, then add the flour and toss well to coat. Pour in the stock and bring to a boil, stirring. Simmer for 2 minutes. Remove the pan from the heat and set aside.
To make the pastry, tear the bread into small pieces and put into a food processor. Pulse until fine crumbs are formed. Add the flour, thyme and vegetable shortening and season with a little salt and pepper. Pulse again to combine, then, with the motor running, pour in enough of the cold water to form a soft dough.
On a lightly floured surface, roll out three-quarters of the dough, to a circle large enough to line a 1 litre pie basin. Line the basin carefully, then fill with the steak and kidney mixture. Trim the excess pastry. Roll out the remaining pastry to form a lid, wet the edges of the dough and place on top of the filling, sealing the edges well with your fingers.
Cover the basin with a double thickness of foil, pleated in the middle and secured with string. Steam the pie over simmering water for 3 hours. Serve the pie hot.
Nutritional Information: 17 g protein, 19 g fat of which 9 g is saturated, 27 g carbohydrate, 4 g fibre, 357 Calories