Preheat oven to 425F. Peel potatoes and cut into thin slices. Cut eggplants into thin slices as well. Grease a large baking sheet with olive oil (you may need to use 2 sheets) and place the eggplant and potato slices on the sheet. Try not to overlap the slices. Place the olive oil into a small bowl, and use it to brush the tops of the eggplant and potato slices. Bake the eggplant and potato slices for 25 minutes, until the tops begin to brown.*

Meanwhile, prepare the tomato sauce. Pour the tomato sauce and diced tomatoes into a large bowl. Add minced garlic, salt, pepper, sumac, cumin, and chopped parsley. Stir thoroughly to combine.

Chop the onion into thin rings or strips. Chop the tomatoes into thin slices.

Once the eggplants and potatoes are browned, remove them from the oven and set aside. Begin to assemble the moussaka for baking. Line a large, deep, baking dish with aluminum foil if desired. Drizzle the bottom with olive oil. Pour ¼ of the tomato sauce mixture on the bottom of the baking dish and spread the sauce around, creating a very thin layer to start off with.

Layer half of the potato and eggplant slices on top of the sauce. Top with half of the onion slices. Then, top with all of the tomato slices. Pour half of the chickpeas over the dish. Pour ½ of the remaining tomato sauce mixture over all of the layers and spread evenly. Layer the remaining eggplant and potato slices over the sauce, reserving a few slices to decorate the top later. Layer the remaining onion slices on top of the eggplants and potatoes. Pour the rest of the chickpeas and tomato sauce over the dish. Top the dish with the few eggplant and potato slices that you reserved.

Add ½ cup water to the baking pan to thin out the sauce a little bit. If it still looks dry, you can add another ½ cup of water. Drizzle the top with some olive oil if desired. Bake for 25-30 mins.

Meanwhile, prepare the roasted pine nuts for topping, if using. In a small saucepan, roast the pine nuts in olive oil for 3-5 minutes. Alternatively, dry toast the pine nuts until slightly browned and fragrant. Watch closely to see when they just begin to brown, and immediately remove from the heat and set aside.