In a Dutch oven, cook cabbage in boiling water for 10 minutes or until outer leaves are tender. Drain and rinse in cold water; drain. Remove eight large outer leaves (refrigerate remaining cabbage for another use) and set aside.
Meanwhile in a large saucepan, saute 1 cup onion in butter/oil until tender. Add the tomatoes, garlic, sweetener and 1/2 teaspoon salt. Simmer for 15 minutes, stirring occasionally.
Meanwhile, in a large bowl, combine the rice, ketchup, Worcestershire sauce, pepper and remaining onion and salt. Crumble beef and sausage over mixture, add in mushrooms and mix well.
Remove thick vein from cabbage leaves for easier rolling. Place about 1/2 cup meat mixture on each leaf; fold in sides. Starting at an unfolded edge, roll up leaf to completely enclose filling. Place seam side down in a skillet. Top with the sauce.
Cover and cook over medium-low heat for 1 hour. Add V8 juice if desired. Reduce heat to low; cook 20 minutes longer or until rolls are heated through and a thermometer inserted in the filling reads 160°.
