Begin by preheating your oven to 180°C (350°F/Gas Mark 4) to prepare for slow cooking the stew to tender perfection. In a large ovenproof casserole, warm the olive oil and butter over medium heat until melted and shimmering. Add the beef chunks and sear them thoroughly, browning on all sides to lock in the juices and develop a rich depth of flavor. Sprinkle the plain flour evenly over the browned beef and continue cooking for an additional 2 to 3 minutes. This step helps to thicken the stew during cooking, creating a silky sauce. Next, stir in the minced garlic and all the prepared vegetables — onions, celery, carrots, chopped leeks, and swede. Fry gently for 1 to 2 minutes to soften the vegetables and awaken their flavors. Pour in the red wine, allowing it to deglaze the pan and lift all those tasty browned bits. Add the beef stock along with the bay leaves and thyme, stirring to combine. Season the mixture with Worcestershire sauce, balsamic vinegar to your taste, salt, and freshly ground black pepper, balancing the savory and tangy notes. Cover the casserole tightly with a lid and transfer it to your preheated oven. Let it cook slowly for around two hours, or until the beef becomes beautifully tender and the flavors meld harmoniously. While the stew cooks, prepare the dumplings. Sift together the plain flour, baking powder, and salt into a mixing bowl. Incorporate the suet, then gradually add enough water to bring the dough together into a thick, workable consistency. With floured hands, shape the dough into small balls roughly the size of a walnut. Keep them ready for the final cooking stage. Once the stew has cooked for two hours, carefully remove the lid and nestle the dumpling balls on top of the stew surface. Replace the lid and return the dish to the oven to cook for an additional 20 minutes, allowing the dumplings to swell and become tender. For those who prefer a golden crust on their dumplings, simply leave the lid off during this final baking period to let them brown beautifully. To serve, spoon a generous portion of mashed potatoes onto each plate. Ladle the rich beef stew and fluffy dumplings over the top, then finish with a sprinkle of freshly chopped parsley for a burst of color and herbaceous freshness. Tip: Ensure your stew remains bubbling gently in the oven by checking the liquid level halfway through cooking. Add a splash of stock or water if it looks too dry to prevent sticking or burning.