1) Toss the onion, carrots, celery and garlic into the food processor, and process until finely chopped; set aside.
2) In a large zip-lock back or a bowl, toss thebeef with the flour, salt, and pepper until evenly cotated.
3) Coat a large nonstick skillet with cooking spray and set it over medium-high heat. When the pan is hot, add the oil, then add half of thebee and brown it on all sides for 3 to 4 minutes. Transfer to a large pot or crock pot. Cook the rest of the beef the same way and add it to the pot.
4) Add the chopped onion, carrot, celery, and garlic to the skillet, reduce the heat to medium, and cook for 6 to 7 minutes or until the vegetables begin to soften. Add them to the pot.
5) Add the beef broth, tomatoes and their juice, brocolli puree, cover, and bring to a boil, then reduce the heat and simmer 4 hours. Add the potatoes and cook until the meat is very tender and begins to fall apart. 4 1/2 to 5 hours total.
(Slow Cooker Modification - Cook on low for 8 hours, then add the potatoes, set on high for 1 additional hour, and serve)