Toss the steak in the seasoned flour and brown in batches in the hot oil. Set aside.
Cook the onions and mushrooms until soft, adding the garlic and tomato purée for the last minute.
Return the beef, add the ale, stock, Worcestershire sauce, bay and thyme and bring to a simmer.
Cover and cook gently for 2 to 2½ hours until the beef is tender and the sauce thick.
Remove the herbs, season and cool the filling for at least 30 minutes.
Preheat the oven to 200°C (180°C fan, gas 6). Fill a pie dish, cover with pastry, brush with egg and bake for 30 to 35 minutes until golden.