How to cut eggplant into slices
For most dishes, eggplant needs to be sliced before it's cooked. There are two basic cuts - rounds, which are great for almost every dish, and planks, which work particularly well for layered dishes like moussaka or vegetable lasagnas.
When choosing eggplants, reach for the smallest ones you can find. Their flesh is usually more tender and less fibrous than the older, larger ones.
Round slices are the most basic cut. They're great for grilling, broiling, and traditional dishes like eggplant parmesan. Remember that eggplant loses moisture and shrinks when cooked. To compensate, cut the raw eggplant into pieces about twice as large as you want the cooked pieces to be.
Lengthwise slices are good for grilling and layered dishes where you want the eggplant to have the most surface area. To make them, first stand the eggplant upright on its end and slice away a section of the peel. This isn't a must, but it gives the end slices more fleshy surface area to take on color and flavor when cooked.
Then just slice down the length of the eggplant to make slices as thick or thin as you like. You can slice away a section of skin on the other side of the eggplant when you're finished slicing.