Season the beef stew meat with salt and pepper.
Heat olive oil in a large, heavy pot over medium-high heat.
Add butter and brown half of the stew meat until golden on the outside, about 2 minutes per batch.
Remove the browned meat and repeat the process with the remaining half.
Once done, set aside all the browned meat.
In the same pot, add chopped onion, diced carrots, and celery.
Cook until the vegetables start to soften, then stir in minced garlic and cook for another minute.
Return the meat to the pot.
Pour in beef stock, red wine, and tomato paste.
Add Worcestershire sauce, bay leaves, thyme sprigs, and mushrooms.
Bring it to a boil, then reduce the heat to low, cover, and let it simmer.
Cook for about 2-3 hours or until the meat is tender and the flavors have melded.
Add fresh parsley before serving.