Sift flour and salt into a bowl and chill in the fridge.
Cube the cold butter.
Stir butter into the flour until pieces are well coated.
Add water and mix rapidly with a knife to form a rough dough.
Shape into a flat cylinder without kneading, wrap in film, and chill for 15 minutes.
Roll pastry into a 45x15cm rectangle about 1cm thick.
Fold the bottom third up and the top third down into a square.
Rotate the dough 90 degrees and seal edges with a rolling pin.
Repeat the rolling and folding process four times.
Chill the finished pastry for at least one hour or overnight.
Toss the beef with flour, salt, and pepper in a bag.
Brown half the beef in oil for 10 minutes in a hot casserole.
Remove beef, deglaze the pan with ale, and brown the remaining beef.
Sauté chopped garlic, onion, carrots, celery, and herbs in oil until soft.
Add meat, stock, ale, purée, and vinegar, then simmer for 1 to 1.5 hours.
Cool the filling completely, ideally overnight.
Fry mushrooms in butter until golden and stir into the filling.
Preheat oven to 200°C and roll out pastry to cover the dish.
Brush the edge of the pie dish with water or egg.
Place the pastry lid over the filling and press to seal.
Pattern the edges with a knife to encourage puffing.
Slit the top for steam and brush with beaten egg.
Chill the pie for 10 minutes until firm.
Bake for 30 minutes until the pastry is golden and filling bubbles.