Prepare the Beef: Pat the beef chunks thoroughly dry with kitchen paper. This step is crucial for achieving a good sear. Season generously with salt and black pepper. In a large, heavy-bottomed stockpot or Dutch oven, heat 1 tablespoon of olive oil over medium-high heat until it shimmers. Add the beef in a single layer, working in batches to avoid overcrowding the pan. Sear the beef for 3-4 minutes per side until each piece develops a beautiful, rich brown crust. You should hear a satisfying sizzle as the beef hits the hot pan. Once browned, remove the beef and set aside on a plate.

Sauté Aromatics: Reduce the heat to medium and add the remaining 1 tablespoon of olive oil to the pot. Add the chopped onions, carrots, and celery. Sauté for 8-10 minutes, stirring occasionally, until the onions soften and turn translucent, releasing a sweet, earthy aroma. Stir in the minced garlic and cook for another minute until fragrant, being careful not to let it burn.

Build the Base: Sprinkle the plain flour over the sautéed vegetables. Stir well and cook for 2 minutes, allowing the flour to absorb the pan juices and toast slightly. This will create a roux that thickens the stew. Gradually pour in the beef stock, stirring constantly with a whisk to scrape up any browned bits from the bottom of the pot and prevent lumps. The mixture will start to thicken, turning into a rich, glossy sauce.

Simmer and Infuse: Stir in the tomato purée, Worcestershire sauce, bay leaves, and dried thyme. Bring the liquid to a gentle simmer. Return the browned beef chunks to the pot, ensuring they are mostly submerged in the liquid. Reduce the heat to low, cover the pot with a tight-fitting lid, and let it gently simmer for at least 2 hours. During this time, the beef will slowly tenderise, becoming incredibly soft, and the sauce will deepen in colour and flavour, filling your kitchen with a truly enticing aroma.

Add Remaining Vegetables: After 2 hours, carefully remove the lid. Add the halved new potatoes and button mushrooms to the pot. Stir gently to combine them with the stew. Re-cover the pot and continue to simmer for another 45-60 minutes, or until the potatoes are fork-tender and the mushrooms have softened, absorbing the rich flavours of the stew. The liquid should be thick and bubbling gently.

Rest and Serve: Once the beef is melt-in-your-mouth tender and the vegetables are cooked through, remove the pot from the heat. Take out the bay leaves. Taste the stew and adjust seasoning with salt and freshly ground black pepper as needed. Let the stew rest, covered, for 10-15 minutes before serving. This resting period allows the flavours to meld further and the sauce to settle. Ladle the hearty stew into bowls and garnish generously with fresh chopped parsley before serving.