If you're planning on making your own sauce instead of using store-bought, you'll need to start by making the sauce first.
Slice the eggplants lengthwise into ¼ inch slices. Set the eggplant slices onto a baking sheet. Pour milk onto the sliced eggplant and soak for 15 minutes. (this step is optional, but it will result in creamy eggplants vs a dried eggplant⏤If you choose to opt-out of this step, just bake a little longer.)
Preheat Oven 450ºF and line two sheet pans with parchment paper.
Remove the eggplant slices from the milk and transfer them onto the prepared baking sheets. Bake for 20 minutes, turning halfway through until eggplant is golden.
Meanwhile, prepare your ricotta mixture. In a medium-sized mixing bowl, add all of the ricotta mixture ingredients. Mix well and set aside.
After 20 minutes of the eggplants baking, remove them from the oven; you may notice they're not fully cooked but slightly softened, and that's exactly what we're looking for.
Prepare your baking dish. Pour ½ cup sauce on the bottom of a 9x12 baking dish and add ⅓ of eggplant to cover the dish's bottom. Top with ⅓ of the ricotta cheese mixture, ⅓ of the mozzarella cheese and ¾ cup of the sauce. Add another layer of eggplant and repeat the ricotta cheese, mozzarella cheese and sauce two more times, reserving the third layer of mozzarella for topping. (you're going to be making 3 layers in total)
Finish with remaining sauce, mozzarella, and the reserved 2 tablespoons of grated parmesan cheese
Cover with foil and bake until cheese is melted and everything is bubbling—about 40 minutes.
Remove foil and continue baking for 10-15 minutes.
Remove from oven and allow the eggplant parmesan to rest for 10 minutes before cutting.