Pre-heat the oven to 350°F (175°C).
Heat a large Dutch oven (I used 5qt pot) over medium high heat. Then add oil.
When oil is shimmering hot, working in batches, add beef chunks in one layer and brown the meat on all sides, 3-4 minutes, removing the seared meat onto a clean plate and continuing with the remaining beef.
Once all the beef is browned, return all the meat back into pot.
Add porcini powder, flour, salt and pepper. Stir well and cook for 2 minutes.
Pour in the stock.
Using a wooden spoon, deglaze the pan by scraping the bottom of the pan.
Cover the pot and place it in the oven. Cook for 1 hour.
Meanwhile, chop the carrots and onion, if using.
Now, add carrots, onion, garlic, bay leaf and thyme.
Add balsamic vinegar and mix everything well.
Cover the pot and cook for 30 minutes, or until vegetables are tender.
Garnish with fresh thyme, if desired, and serve along with bread to soak up all the gravy. You can also serve the stew over mashed potatoes, polenta, or barley.