Set out the flour in a plate or bowl, 3 eggs and the milk or water in a bowl and the panko, 1/2 teaspoon salt, black and crushed red pepper flakes in another plate or bowl. Dust each eggplant slice with flour, gently knocking off the excess, then dip it in the egg and milk or water mixture, and finally coat it with the panko.
Put the slices on two parchment or silicon mat-covered sheet pans and drizzle them with half the olive oil. Bake for 15 minutes and turn them. Drizzle the slices with the rest of the olive oil and bake for another 10-15 minutes to brown them.
When done, set the eggplant slices aside and turn the oven down to 375 degrees.
Mix the ricotta, leftover egg mixture from the eggplant and the additional egg, plus the dried oregano.
Using a 9 inch x 13 inch baking pan, layer the eggplant, sauce and slices as follows
1/2 cup of sauce
1 layer of eggplant slices
1 cup of sauce spooned over the slices
Slices or 1-2 handfuls of mozzarrella distributed as evenly as possible
1/2 of the ricotta and egg mixture spooned over the mozzarella
1/3 cup parmigiana cheese sprinkled over the ricotta mixture
Repeat
End with mozzarella and parmigiana
Bake for about 30 minutes, until the cheeses are melting and the top begins to brown.
Let the casserole sit outside the oven for 5-10 minutes before cutting into it.
Recipe Notes
Romano is a good alternative to parmigiana (also known as parmesan) cheese. If baking the casserole in a toaster oven, you'll need to use the toaster oven tray and will only be able to fit about 1/3 of the casserole onto the tray. (It's easiest to make it in the 9" x 13" baking pan and transfer as many pieces as will fit easily onto the toaster oven tray. Put the rest away, either in the refrigerator or freezer for later.