In a small saucepan saute onion in 1-tbsp olive oil, then add tomato sauce and warm set aside. Pare 1 large eggplant (about 11/2 lbs) and cut crosswise into 1/4 inch thick slices. Dip slices into beaten eggs, then into seasoned crumbs.
Saute eggplant slices in 1/2 cup olive oil for about 3 minutes on each side. Drain well. In a 8x12-inch baking dish, layer half of eggplant; top with half of tomato sauce and 1/2 lb. mozzarella cheese (grated). Repeat, sprinkle with parmesan cheese.
Cover and refrigerate till ready to use. Then bake uncovered at 325 for 30-40 minutes, or until cheese is melted and sauce is bubbly.