Preheat oven to 230°C. Place the pork in a frying pan and saute slowly in a tablespoon of Heritage Virgin Olive Oil for five minutes, or until lightly browned.
Remove the diced pork and set aside. Heat the leftover fat until it's very hot (but not smoking).
Dry beef with paper towels, and add it to your frying pan in batches Brown nicely on all sides, regulating heat so the fat is always very hot (but, again, not smoking).
Transfer meat to a casserole dish. Add two tablespoons of flour to the meat in casserole.
Stir and place in your oven for four minutes. Stir again, and return to the oven for a further four minutes.
Reduce heat to 160°C. Add the sliced carrots to the frying pan and brown over medium heat.
Transfer carrots to your casserole mix, and 'wash' frying pan with 200ml of wine.
Add wine to the casserole along with the beef, wine, beef stock, diced pork, tomato paste, garlic, and mixed herbs.
Bring to simmer and salt lightly if needed.
Place in oven for 2 - 3 hours, checking every 15 minutes after one-and-a-half hours have passed.
Place your onions in a heavy saucepan along with some water (just enough to cover them), a pinch of salt, and the diced pork. Cover and simmer slowly, tossing occasionally for about 30 minutes, or until onions are just tender when pierced with a knife. Set aside.
Halve or quarter mushrooms, and fry in a saucepan with some oil. Add to the cooked onions. Set aside the onions and mushrooms until stew has completed.
When the beef is tender, set a large colander over a saucepan and pour the contents of casserole into colander.
Wash out the casserole and return the beef to it.
Press juices out of remains in colander and discard the residue.
Skim fat off cooking liquid in saucepan.
Make a buerre blanc by whisking together the flour and softened butter. Whisk the buerre blanc into the sauce. Bring to a boil while stirring.
Simmer for 2 - 3 minutes.
Add the onion and mushroom mixture to the beef, and add the sauce to the mixture.