To prepare the sauce: Heat a 2 1/2-quart saucepan over medium heat and when hot, add 3 tablespoons oil. When oil is hot, stir in minced onion, green and red pepper, celery and garlic. Cook over medium-low heat until vegetables are softened and fragrant, about 4 to 5 minutes. Stir in tomato puree, tomato paste, ketchup, vinegar, molasses and Worcestershire sauce. Bring mixture to a simmer and turn heat down to very low. Simmer sauce with the cover ajar for 1 hour. Meanwhile, heat an 8-inch skillet over high heat and when hot, add 1 tablespoon extra-virgin olive oil. When oil is hot, add chopped mushrooms and cook mushrooms, stirring over high-heat until golden, 2 to 3 minutes. Turn heat off and set skillet aside. After sauce has been simmering for 1 hour, uncover and add Sauteed chopped mushrooms, prepared fresh tomatoes, oregano, Bovril seasoning and some freshly ground black pepper. Bring back to a simmer and cook with the cover ajar for 30 minutes more. Uncover and let cool until needed.
Note: If you plan on cooking right away, just measure out 2 cups of the sauce, and let the remaining sauce cool. Freeze for the next time.
To add browned ground meat: Heat a 10-inch deep-sided skillet over medium heat and, when hot, add the ground meat and break up with a wooden spoon. Cook meat until separate and golden brown, then remove from the stove and drain out any excess fat from skillet. Return pan to stove and stir in 2 generous cups of prepared sauce to meat. Bring mixture to a gentle simmer over low heat and cook (uncovered) until flavors mingle and the mixture is piping hot throughout, about 10 minutes. Add some more freshly ground black pepper to taste and
Note: If serving 4, brown 1 pound of ground meat and add 1 generous cup of sauce.
To assemble Sloppy Joe's and serve: Spoon ground beef mixture onto split hamburger buns that have been spread lightly with butter and broiled to toast the buttered side only. Serve hot.
This Sloppy Joe mixture is not only great on buns, but it's also fabulous over hot (lightly buttered) pasta. Toss in some cooked peas (fresh or frozen) and you've got yourself a hearty and delicious meal. Alternatively, stir this into a bowl of cooked long grain white rice, for a change of texture.
And don't throw out any leftovers...heat it up the next night and spoon it onto baked potatoes. Eat (as is) or if desired, sprinkle the top lightly with grated cheddar cheese and broil until the cheese is melted and bubbling. Now, add a simple green tossed in a light vinaigrette and you've got yourself yet another easy and delicious meal!