Tip the beef into a large bowl with the bay leaves, thyme, stock and a generous pinch of pepper, then cover and leave in the fridge overnight.
Preheat the oven to 140°C / 275°F / Gas mark 1.
Place a colander over another large bowl and strain the marinated meat, reserving the stock.
Heat half of the oil in a large frying pan then brown the meat in batches, transferring to a plate once browned.
When all the meat is browned, pour a little stock into the empty frying pan and bubble to release any caramelised bits from the pan.
Heat the rest of the oil in a large casserole dish and fry the carrots and chopped onions until they start to colour.
Stir in the flour for 2 minutes, then add the tomato purée.
Add the beef and any juices, the stock from the frying pan and the rest of the stock and herbs.
Season with salt and pepper and bring to a simmer.
Stir well to combine then cover either with a lid or kitchen foil.
Transfer to the oven and cook for 6 hours until the meat is really tender.
Allow to cool.
To serve, heat the butter in a frying pan then add the bacon and onions.
Sizzle for about 10 minutes until the bacon starts to crisp and the onions soften and colour.
Add the mushrooms and fry for another 10 minutes, then stir everything together and heat for 20 minutes more.
Serve scattered with chopped parsley and the peppercorns if using.