Water buffalo are now farmed in the UK. Their meat makes a delicious alternative to beef: it's lean and cooks to a lovely tenderness, with a rich flavour. If you can't get hold of buffalo, you can use good stewing beef such as braising or chuck steak (simmer it for about twice as long before putting in the pie).
Make the flaky pastry following the step-by-step recipe on page 000. Wrap the dough in cling film and leave to chill in the fridge while you make the filling.
Put the flour in a large bowl and season it well with salt and pepper. Toss the meat in the flour until evenly coated.
Heat 1 tbsp oil and the butter in a flameproof casserole over a medium-high heat. Working in batches, brown the meat well all over, adding a dash more oil if you need to. Transfer the browned meat to a dish.
Lower the heat under the pan, add a little more oil if necessary and add the shallots and carrots. Sauté for a couple of minutes, until the shallots are just starting to soften. Return all the meat to the pan. Add the mushroom ketchup and tomato purée and cook for another 2 minutes.
Pour in the ale and stock, then add the thyme and sugar. Bring to the boil, then reduce the heat, cover with a lid and simmer gently for an hour or until the meat is very tender.
Transfer the meat to a 1.5 litre pie dish and leave to cool completely. (If there is a lot of liquid, keep some of it back to serve as gravy).
On a floured surface, roll out the pastry to a 3mm thickness. Cut a 2cm strip of pastry. Dampen the rim of the pie dish with water and press the pastry strip onto the rim. Cut the remaining pastry a little larger than the pie dish. Sit a pie funnel in the centre of the filling. Press the lid over the top and crimp the edges. Trim away the excess pastry.
Brush the pastry with beaten egg and make a steam hole exposing the funnel. Bake for 35–40 minutes until the pastry is crisp and golden. Leave to settle for 10–15 minutes before serving.