Meanwhile, gently heat 1 tbsp of the oil in a large pan and cook the onion and garlic for 10 minutes until soft but not coloured.
Remove with a slotted spoon and set aside.
Toss the steak in the flour, add to the pan along with the remaining oil, increase the heat and brown all over, in batches if necessary.
Return the softened onion and garlic to the pan with all the steak.
Add the thyme and bay leaf, pour over the ale and stock, then stir in the mustard and Worcestershire sauce.
Bring to the boil, cover, then simmer gently for about 1 hour 45 minutes until the meat is tender.
Remove and discard the bay leaves and thyme sprigs.
Transfer the pie filling to a bowl and cool completely.
