Peel the onions and slice them thinly, first halving them lengthwise, then cutting crosswise into fine slivers. Set aside while you prepare the beef.

In a large Dutch oven or heavy-bottomed braising pot, heat the olive oil over medium-high heat. Working in batches, sear the beef pieces on all sides until they develop a deep, golden-brown crust. Take your time to ensure even browning—this step builds the base of the stew’s rich flavor. Transfer the browned meat to a plate and season generously with salt and pepper.

If too much fat remains in the pan, drain off the excess, leaving just a thin layer. Pour in the white wine and bring it to a lively boil, scraping up all the caramelized bits from the bottom with a wooden spoon or silicone spatula. Allow the wine to bubble and reduce for about 7 minutes, cooking off some of the alcohol and concentrating its flavor. Whisk in the Dijon mustard until fully blended.

Return the seared beef and any juices from the plate to the pot. Add the canned tomatoes with their juices, gently crushing them with your hands as you add them. Stir in the sliced onions, smashed garlic cloves, and the bouquet garni. Mix everything together, ensuring the meat is well-coated and submerged in the liquid. Cover the pot and let the stew simmer slowly over very low heat for 2 to 3 hours, or until the beef becomes tender enough to fall apart with a fork. Keep the simmer gentle to preserve the meat’s moisture and flavor.

Once the beef is tender, remove the bouquet garni and bay leaves. Lift the meat and vegetables out with a slotted spoon and set them aside. Increase the heat and bring the remaining sauce to a boil, allowing it to reduce by about one-third to thicken and concentrate the flavors—this should take roughly 10 minutes. If using carrots, add them at this stage and cook them in the sauce until tender.

Return the beef and vegetables to the pot, stirring gently to coat everything in the rich, velvety sauce. Warm through before serving.

Serve the Beef Daube in wide, shallow bowls alongside creamy mashed potatoes, buttered egg noodles, or soft polenta. A slice of crusty bread is perfect for soaking up the luscious sauce.