Cook pasta according to package directions. Meanwhile, in a large skillet, saute mushrooms and onion in 1 tablespoon butter until tender.
In a large bowl, beat ricotta and 4 ounces cream cheese until blended. Stir in 1/2 cup Asiago cheese, Parmesan cheese,1 tablespoon parsley, garlic salt,pepper and mushroom mixture. Spoon into shells; place in a greased 13-in. x 9-in. baking dish.
In a large saucepan, melt remaining butter. Wisk in flour until smooth; gradually add the cream, broth and milk. Bring to a boil; cook and Wisk for 1-2 minutes or until thickened.
Stir in Romano cheese and the remaining cream cheese, Asiago and parsley,wisk untl smooth and melty. Pour over shells. Sprinkle with mozzarella cheese. Cover and bake at 350° for 30 minutes. Uncover; bake 10-15 minutes longer or until bubbly.
In a large bowl, combine the beef, onion,1 clove of chopped garlic, cereal crumbs, milk, egg, 2 tablespoons parsley and 1 teaspoon salt; shape into eight 2-in. balls.
In a large saucepan, heat 1 tablespoon olive oil over medium heat. Add 2nd chopped garlic clove and cook until golden, about 2 minutes. Add the marinara sauce and bring to a simmer, stirring occasionally. Submerge the meatballs in the sauce; bring to a simmer and cook, covered and stirring occasionally, for 20 minutes or until done. Season with about 1 teaspoon salt, or to taste