Spread about 1 big ladle of the sauce in the bottom of a casserole pan.
Arrange the eggplant slices over the sauce, overlapping slightly.
Spoon more sauce over the eggplant and sprinkle generously with Parmigiana cheese.
Arrange another layer of eggplant slices evenly on top.
Add the cut up sausages or mortadella and place the sliced up mozzarella over the sausages.
Spread sauce on top and sprinkle with parmigiana.
Layer the remaining eggplant slices on top and top with the remaining sauce.
Generously and evenly sprinkle the Parmesan on top.
Bake uncovered, until the sauce bubbles and the top is golden, about 25 to 35 minutes.
Let it cool for at least 15 minutes to give it time to set.
Cut with a knife, plate and enjoy!