Trim any large pieces of fat from around the roast.
Pat the meat dry. Season it with salt and pepper.
Let it sit out at room temperature for 15-20 minutes provided it’s cool in your kitchen.
Heat the olive oil in a large, heavy pot over medium heat (see note 1).
When the oil is hot, add the chuck roast. Cook the meat for 5-6 minutes, or until browned. (see note 2)
Turn the roast and cook for another 5-6 minutes until it’s browned on both sides.
Take the pot off the heat and remove the roast. Place it on a pan or plate. Cover loosely with aluminum foil to keep it warm.
Do not wash or wipe the pot. Place it back over medium heat and add the onions, carrots, and celery. Cook the vegetables for 5 minutes until the onions start to soften. Stir often.
Next, add the garlic. Cook for 1 minute while stirring.
Add the onion soup to the sauteed vegetables while stirring and gently scrapping any bits off the bottom of the pot.
Return the chuck roast to the pot along with any juices collected on the plate or pan.
Add enough water so that at least three-quarters (¾) of the roast is covered with liquid at its thickest part.
If the onion soup broth does not come to a simmer right away, then raise the heat. When it starts simmering lower the heat to medium-low and cover the pot. Keep the liquid at a simmer during the cooking time, raise or lower the heat as needed.
Cook the roast with onion soup for about 2½ hours or until it’s almost fall-apart tender. Check on it every ½ hour or so, especially after raising or lowering the heat to make sure the liquid is simmering how we want it.
Add the potatoes to the pot. Arrange them around the beef roast. Make sure that they are submerged in the onion broth. Raise the heat and let the liquid come back to a simmer. Then, lower it to medium-low. Cover the pot and cook the meat and potatoes for another 20-30 minutes until they are both tender. A fork or a knife should slide in and out without them offering any resistance.
Serve the roast with the potatoes and sauce. Garnish with chopped parsley, if desired. Enjoy with a generous piece of crusty bread to soak up the delicious broth.