The best and easiest way to get the beef as thin as needed is to ask your butcher to slice it across the grain and 2-3mm (1/16th inch thick).
Heat oven to 350°F (for the bread bowls).
Season the beef with kosher salt and freshly ground black pepper. Set aside.
Heat a large skillet over medium heat and add the oil and butter. Add the onions and green pepper and cook 3 minutes or until softened.
Add sliced mushrooms and cook and additional 3 minutes or until mushrooms have softened. Add the garlic and cook another 30 seconds – just long enough for the garlic to bloom and become fragrant. Transfer the vegetable mixture to a separate bowl and set aside.
If needed, heat a little more oil to the skillet and add enough meat just to cover the inside of the skillet. Brown the beef on both sides, about 1 minute per side (the beef may still be a little pink inside). Transfer the beef to a paper towel-lined plate, and repeat until all beef is browned.
With the heat set to medium-low, slowly add the wine while deglazing (scraping the browned bits off) the pan. Add the beef broth, French onion soup and Worcestershire Sauce. Stir well.
Add the vegetables and the beef back to the pot and bring to a boil.
Reduce the heat to low and simmer 30-60 minutes to thicken the soup.
(*Note – while the soup cooks, make the bread bowls.)
Add the heavy cream and simmer an additional 15 minutes, stirring often so the cream won’t scorch.
When ready to serve, fill each bowl with soup and top with 1 slice of provolone or mound with shredded provolone.
Set oven to broil and place the bowls of soup on the middle rack. Watch the soup carefully, so the cheese doesn’t burn. Broil until the cheese has melted and just beginning to toast.
For the Bread Bowls:
Cover a baking sheet with aluminum foil.
Use a serrated knife to cut ½-1 inch (depending on the size of your bread) off the top of the loaf.
Hollow out the inside of the loaf, leaving about a 1-inch edge of bread around the perimeter.
Place the bread bowls and their tops on the prepared baking sheet and brush the insides, the edges and the tops of the bowls with olive oil.
Bake for 15 minutes or until golden brown. Remove from the oven and set aside while soup cooks.