In a broad, shallow dish, mix the flour, 1 teaspoon of salt, and 1 teaspoon of black pepper. Dredge each beef piece in the flour mixture, ensuring an even coating. Shake off any excess flour.

Heat half of the vegetable oil in a large Dutch oven over medium-high heat for about 2 minutes, or until it begins to shimmer. Brown the beef in batches, adding more oil as needed, until each piece is golden-brown on all sides. Transfer the browned beef to a plate and continue until all pieces are seared.

Add the minced garlic and tomato paste to the pot, stirring constantly for around 2 minutes until it transforms into a deep, reddish-brown hue. Pour in the apple cider vinegar and Guinness, stirring vigorously to release the browned bits on the bottom of the pot.

Return the browned beef to the pot, adding the beef broth, bay leaves, rosemary, thyme, and the remaining salt and pepper. Raise the heat to bring the mixture to a gentle boil, then reduce it to a bare simmer, partially covering the pot. Allow it to cook slowly for 2 and 1/2 hours, stirring occasionally. Ensure the stew maintains a low, gentle simmer throughout.

Stir in the brown sugar, onions, potatoes, and carrots, continuing to simmer for an additional hour, or until the vegetables reach tenderness.

In a small cup, combine the cornstarch with water until smooth, then pour this mixture into the stew. Stir well and cook for about 5 minutes, or until the broth thickens slightly. Adjust the seasoning with salt and pepper to taste.

Serve hot, ladled into bowls, and sprinkle with freshly chopped parsley for garnish. Enjoy!