Preheat the oven to 230C/210C fan/gas 8.
Bring 1 litre of water to a simmer in a medium saucepan, add the bacon rind and pieces and simmer for 10 minutes. Drain and pat dry with kitchen paper.
Heat half the olive oil in a large casserole over a medium-high heat, add the bacon pieces and fry for 2-3 minutes until golden-brown. Remove from the casserole and set aside.
Pour in the remaining olive oil and add about half of the beef, taking care not to overcrowd the pan or the meat won't brown. Cook the beef, without stirring, for 2-3 minutes, or until a dark golden-brown on one side, then stir and brown on all sides. Remove from the pan and add to the bacon, then repeat with the remaining beef.
Add the carrots and onions to the casserole and fry for 3-4 minutes, or until golden-brown, then return the bacon and beef, along with any juices, to the casserole.
Season with salt and black pepper and stir in the flour, making sure it is well mixed in and absorbs the juices. Transfer to the oven for 5 minutes then give it another stir and return to the oven for a further 5 minutes.
Remove the casserole from the oven and reduce the oven temperature to 170C/150C fan/gas 3. Place the casserole over a high heat and pour in the wine and stock to just cover the meat. Stir in the tomato paste, garlic, thyme, bay and bacon rind and bring to a simmer, then cover the casserole and return to the oven.
Cook for 3-4 hours, or until the meat is meltingly tender. Check every hour or so that there is enough liquid, topping up with a little more stock or boiling water if necessary, 9. While the casserole is cooking, pour the beef stock into a small saucepan over a medium heat and add the baby onions. Cover and bring to a boil, then reduce the heat to low and simmer the onions for 15-20 minutes, or until just tender. Keep warm. Alternatively you can omit the beef stock and stir the raw onions into the casserole for the final hour of cooking.
Melt the remaining butter in a frying pan over a medium heat and fry the mushrooms for 5 minutes, until just tender and golden-brown. Set aside.
. When the beef is cooked, strain the contents of the casserole through a colander into a large bowl. Wash and dry the casserole and tip the contents of the colander back into the casserole.
. Pour the cooking liquid from the bowl into a medium saucepan and bring to the boil over a high heat. Boil for about 5 minutes, or until to reduced to a rich sauce consistency. Pour the sauce over the beef, stir in the cooked onions and mushrooms and bring to a simmer over a medium heat.
. Sprinkle with parsley and serve.