Heat 3 tablespoons olive oil in a large frying pan or a large pot, then add sliced onions and cook on a medium heat until softened, around 5 minutes. Add minced garlic cloves and cook for 2-3 minutes more, then add 3 tablespoons butter.
Once the butter is foaming a little, add sliced mushrooms and cook for around 5 minutes.
Add the beef to the pan and cook for 3-4 minutes, until beef is no longer red but brown. Season with freshly ground pepper.
Add all the remaining ingredients except cornstarch, cooking cream and parsley, reduce heat and simmer for 45-60 minutes or until beef is tender.
When beef is tender and the sauce is thick, increase heat to medium high and add cornstarch, fresh parsley and cooking cream. Mix well and cook for 1-2 more minutes.
Garnish with more chopped parsley, and serve with pappardelle pasta, rice or creamy mashed potatoes.
