Place the oil in a casserole dish over a high heat. Dice the beef and add to the pan to brown on all sides - it's easiest if this is done in batches. Once cooked, transfer the meat to a separate plate.
Cut the bacon into small pieces and add to the pan with the onion and garlic. Fry the bacon until it starts to brown.
In a separate wide-based pan, pour in the wine and boil to reduce by half.
Sprinkle the flour over the onion,bacon and garlic mixture and then pour over the reduced wine, brandy and beef stock. Stir until combined and thickened, and bring to the boil.
Add the remaining stock, return the meat to the pan, season with salt and pepper and add the thyme.
Bring to the boil, then cover with a lid and place in the oven for 1hr 30 mins to 2 hrs.
Just before the beef is done, cut up the mushrooms in hald and fry over a medium heat with a knob of butter for about 2 mins.
Peel the pickling onions and add them to the pan, tossing together.
Add the mushrooms and onions to the casserole and then continue to cook for another 40 mins, or until the meat is completely tender.
Sprinkle with parsley and serve immediately, perhaps with some mashed potato and carrots.