Cut the onions into not too thin slices, mince the garlic cloves.
Add butter to a frying pan and fry the meat chunks until browned. Add the onion now.
Fill the herbs and spices into a tea egg so you can easily remove them at the end.
Add the dark beer and all the spices in the tea egg.
Cover the pot and let it simmer on low heat 2 - 3 hours until the meat is tender.
Uncover the pot, add the mustard and place the slices of bread on top of the dish. Let it simmer until the desired thickness of the stew is reached. The bread will slowly dissolve and thicken the dish.