Wash and pat dry the beef leg slices, then season with salt and pepper. Peel and cut the carrots in half lengthways, then cut into 1 cm thick pieces. Clean the mushrooms with paper towels and cut in half. Peel the onions and cut into large cubes. Peel the garlic cloves and leave whole. Drain the pickled green pepper and roughly chop.
Coat the beef leg slices in flour on all sides. Fry in hot oil over medium-high heat for 2-3 minutes per side until browned. Remove and set aside.
Melt the butter in the same pan. Add the vegetables and mushrooms and fry over high heat for 2-3 minutes.
Add the tomato paste and roast for 1-2 minutes.
Deglaze the pan with the white wine and stock, scraping up any browned bits.
Return the beef leg slices to the pan with the pickled green pepper, bay leaves, and rosemary. Cover and cook over low heat for 80-90 minutes until the beef is very tender.