Rëndsziwwelen (beef with onions)

Instructions

1. Cut the beef into thin slices about 1 cm thick, then season them with salt and pepper.
2. Finely slice the onions. Melt the butter in a casserole over medium heat and sweat the onions for 10 to 12 minutes until translucent and golden.
3. Remove the onions, then brown the meat in batches in the same casserole, 2 minutes per side.
4. Return the onions and meat, sprinkle with flour and stir for 1 minute.
5. Deglaze with the white wine, scraping the bottom, then add the stock, bay leaves, thyme and mustard.
6. Cover and simmer gently for 45 minutes, until the meat is tender and the sauce thickened. Adjust the seasoning and serve with potatoes and parsley.