In a large bowl, dissolve yeast in warm water. Add the milk, sugar, shortening, egg, salt and 2 cups flour. Beat until smooth. Stir in enough remaining flour to form a soft dough.

Turn onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to grease the top. Cover and let rise in a warm place until doubled, 1 to 1-1/2 hours.
In a large bowl, combine the milk, eggs, oats, saltines, onion, celery and seasonings. Crumble beef over mixture and mix well. Shape into 1-1/2-in. balls. In a large skillet over medium heat, cook meatballs in batches until no longer pink.

Meanwhile, place tomatoes and onion in a small saucepan. Bring to a boil. Reduce heat; simmer, uncovered, for 10 minutes or until slightly thickened. Stir in the Parmesan cheese, herbs and salt.
Punch dough down. Divide into three portions. Roll two portions into 11-in. circles; line the bottoms and press partially up the sides of two greased 9-in. springform pans. Roll third portion into a 12-in. x 10-in. rectangle; cut into twelve 10-in. x 1-in. strips.

Place meatballs in prepared crusts; top with tomato mixture and mozzarella cheese. Make a lattice crust with strips of dough; trim and seal edges. Cover and let rise for 30 minutes. Bake at 350° for 30-35 minutes or until golden brown. Cut into wedges. Yield: 2 tortes (6 servings each).