Season the meat with salt and pepper and mix with the flour.
Heat the oil and fry the meat in it. Chop the onions and add them. Add the beer. Stir in mustard, tomato paste, bay leaf, herbs and sugar. Season to taste with salt and pepper and simmer over medium heat for approx. 1.5 hours.
Cut the mushrooms into slices. Fry in butter and season with salt and pepper. Add to the meat 5 minutes before the end of the cooking time.