Trim and cut the beef into 1 1/2-by-1/2-inch pieces. In a paper or plastic bag, combine the flour, salt, and pepper. Add the beef to the bag, and shake to coat. Set aside.
Cube the salt pork. In a heavy, medium non-reactive pan over medium-high heat, cook until browned, 6 to 8 minutes. With a slotted spoon, transfer to a small bowl and set aside.
To the same pan, add the carrots and half of the diced onions. Cook, stirring occasionally, until the vegetables are lightly browned, 8 to 10 minutes. With a slotted spoon, transfer them to a small bowl and set aside.
To the same pan over medium-high heat, add 2 tablespoons of the olive oil. Cook the beef in batches, until browned on all sides, 6 to 8 minutes. Return the beef to the pan. Add the wine, 2 1/4 cups of the beef broth, the bay leaves, garlic, celery, and herbes de Provence. Reduce heat to medium. Cover and cook until the beef is tender, 1 1/4 to 1 1/2 hours. Do not allow the liquid to cook away. Add additional broth, if necessary.
Meanwhile, in a small saucepan filled with boiling water, blanch the pearl onions for 1 minute. Drain and let cool. Peel the onions and set aside.
Cut the caps off of 12 mushrooms and set aside. Finely dice the stems along with the remaining mushrooms. Set aside.
When the beef is tender, add the reserved salt pork, pearl onions, and mushroom caps. Cook until the mushroom caps are tender, 15 to 20 minutes. Discard the bay leaves. Keep the stew warm until ready to serve.
In a medium skillet over medium-high heat, heat 2 tablespoons of the olive oil. Cook the remaining diced onion and the bell pepper, stirring occasionally, until the onion turns golden, 4 to 5 minutes. Add the diced mushrooms, and cook until tender, 3 to 4 minutes. Season with additional salt and pepper. Set aside.
To prepare the couscous, in a medium saucepan over medium heat, bring the remaining cup of beef broth and tablespoon of olive oil to a boil. Add the couscous in a stream. Stir once. Remove from the heat. Cover and let stand until couscous is tender, 12 to 15 minutes. Combine the couscous with the mushroom-vegetable mixture.
Lightly oil a 6-cup light mold. Spoon the couscous into the mold and pat down firmly. Invert the mold onto a large serving platter. With a slotted spoon, transfer the beef to the center of the ring. Spoon half of the wine sauce over the beef. Arrange the pearl onions and mushroom caps around the base of the ring. Garnish with parsley. Serve with the remaining sauce on the side.
Recipe courtesy of Couscous by Kitty Morse, Chronicle Books, image courtesy of Alison Miksch