Preheat oven to 350 degrees. In a large saute pan or skillet, add ground beef, onion, celery, and garlic; cook over medium heat until meat is browned; drain liquid. Do not return to heat. Stir in tomato sauce, vegetables, bay leaves, thyme, marjoram, and black pepper. MASHED POTATOES: Boil potatoes over high heat until soft; drain. Add butter and gradually add milk while mashing potatoes with electric mixer or hand masher. The consistency of mashed potatoes should be firm; add milk, as necessary, but remember not to make the potatoes too runny. Set aside. Transfer meat and vegetable mixture to a 22.5-quart casserole. Evenly top with mashed potatoes. Sprinkle with paprika. Cover and bake for 20 minutes or until potatoes are lightly browned.