Season the beef pieces with salt and pat them dry. Heat olive oil in a large heavy pot over medium-high heat, then add the beef in batches, allowing each piece to brown deeply on multiple sides without overcrowding the pot.

Add the minced garlic and cook briefly until fragrant. Pour in the beef stock, water, stout beer, red wine, tomato paste, sugar, thyme, Worcestershire sauce, and bay leaves, stirring to combine everything. Bring the mixture to a gentle simmer, then reduce the heat to low, cover, and let it cook slowly while stirring occasionally.

In a separate pan, melt the butter over medium heat and sauté the chopped onions and carrots until the onions become golden and tender. Set the vegetables aside until the beef has simmered for a while.

Add the sautéed onions, carrots, and diced potatoes to the stew along with black pepper and additional salt if needed. Continue simmering uncovered until the beef is very tender and the vegetables are fully cooked. Remove the bay leaves, skim excess fat if desired, then ladle into bowls and finish with fresh parsley before serving.