For tomato sauce, in medium saucepan, cook onion and garlic in 2 T of oil till tender. Stir in undrained tomatoes, tomato paste, bay leaf, parsley 1/2 t salt, oregano and pepper. Bring to a boil and reduce heat, simmering gently. Simmer uncovered, while you are frying up your eggplant, stirring occasionally. Disgard bay leaf.
Combine flour and 1/2 t salt. Dip eggplant slices into beaten egg, then into flour mixture. In a large skillet brown eggplant, half at a time, in 1/2 cup hot oil about 3 minutes on each side, adding additional oil as needed. Drain well on paper towels.
Arrange a single layer of eggplant in bottom on a 8" x 8" baking dish. Top with 1/2 of the parmesan cheese, half of the sauce and half of the mozzarella cheese. Cut remaining mozzarella into triangles. Repeat the layers of eggplant, parm, sauce, and mozzarella. Bake uncovered, in 400 degree oven for 15 - 20 minutes, till heated through.