Lay the sliced eggplant on a flat tray and salt it well. Place the tray on an incline so that the bitter juices that precipitate will roll off. This will take around 20 minutes. Rub the eggplant with a damp towel to clean off most of the salt, applying some pressure so as to squeeze out the last of the juices.
Fry the eggplant slices in the oil a few at a time. Place on a clean dry towel to soak up the excess oil. Allow the eggplant to cool.
In a 9 x 12 x 3-inch casserole, spoon a small coat of tomato sauce. Lay down a single layer of eggplant, followed by a layer of sauce, chorizo then mozzarella slices, and a sprinkling of parmesan. Repeat the process until eggplant and mozzarella are used up. Finish with a double layer of mozzarella on top. Bake at 375 for around 30-40 minutes, making sure that cheese on top is melted and browned nicely.
