In a heavy bottomed pan, add the carrot, onion, and celery and cook over a medium to high heat for about 5 minutes, or until the veggies start to soften.
Add in the rosemary, thyme, and garlic and cook for a minute.
Sprinkle in the flour, stir well and cook for a further minute before pouring in the Guinness, beef stock, and adding the soft brown sugar.
Add the beef directly into the sauce and stir well. Cover with a lid and simmer over a medium heat for about 3 hours, or until the beef is tender.
Season with salt and pepper, and then add in the balsamic vinegar. Stir well, then transfer it into an oven proof dish.
Preheat the oven to 200C Fan.
For the mash topping, peel and chop the potatoes and add to a pan of salted water. Bring to the boil, then simmer until the potatoes are fork tender.
Drain them, leave them to steam dry, then mash with the butter and milk. Taste for seasoning.
Spoon the mash over the top of the beef, then rough it up with a fork.
Bake it for 20 minutes, or until golden and crisp. Then dish it up and enjoy.