To make the flaky pastry, combine the flour and salt in a large bowl. Put the butter and lard in a separate bowl, mixing them together loosely.
Take one quarter of the mixed fats and rub them into the flour lightly with your fingertips.
Combine the lemon juice with 130ml/4fl oz water and mix lightly into the flour to form a very soft dough.
Roll out the dough on a well-floured surface to a rectangle, about 10x30cm/4x12in.
Take another quarter of the mixed fats and dot evenly over the top two-thirds of the pastry rectangle.
Now fold the empty bottom third up and the top third down over it, as if folding a letter.
Turn the dough 90 degrees and seal the edges by pressing down with your fingers.
Roll out the dough and repeat the dotting and folding three times to use all of the fat.
Wrap the dough in cling film and leave to chill in the fridge for at least 30 minutes before rolling out and using.
To make the filling, put the flour in a large bowl and season it generously with salt and pepper. Toss the meat in the flour until evenly coated.
Heat a tablespoon of 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. Fry gently 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 two 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/2½ pint pie dish and leave to cool completely. (If there is a lot of liquid, keep some of it back to serve as gravy).
Preheat the oven to 200C/400F/Gas 6.
On a floured surface, roll out the pastry to 3mm thickness (about the thickness of a £1 coin).
Cut off a 2cm/1in 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-brown. Leave to settle for 10-15 minutes before serving.