1. Preheat the oven to 150°C/300°F. Place the flour in a large bowl. Add the beef and toss until lightly coated in the flour.
2. Heat 2 tablespoons of the olive oil in a large Dutch oven over low to medium heat. Working in batches, brown the beef on all sides, adding more olive oil if needed. Don’t overcrowd the pot – you want the beef to brown rather than steam. Transfer the browned beef to a plate and set aside.
3.  Add the onions and cook for 6–8 minutes, stirring occasionally, until softened.
4. Add the garlic, carrot, parsnip and celery and cook for another minute.
5. Gradually pour in the beef stock, stirring and scraping up all those lovely browned bits from the bottom of the pot. Add the tomato paste, porcini powder, bay leaves, rosemary and thyme and stir to combine.
6. Return the beef to the pot, along with any juices that have collected on the plate. Stir everything together and bring the stew to a gentle simmer on the stovetop.
7. Cover the Dutch oven with the lid and transfer to the preheated oven. Cook for 2 hours.
8. Remove the Dutch oven from the oven and stir through the Worcestershire sauce and button mushrooms. Return to the oven, uncovered, for a further 1 hour, or until the beef is beautifully tender and the vegetables are cooked through.
9. Remove and discard the bay leaves and rosemary sprigs. Taste and season with sea salt flakes and freshly ground black pepper as needed.

Serve the beef stew hot with creamy mashed potatoes and a good hunk of crusty bread for mopping up all that rich gravy.