There are some things to keep in mind when shopping for eggplant, in particular for this recipe. Look for one that is a deep purple and has glossy skin. It should be nice and firm to the touch with no mushy spots to it and has some weight to it. When considering your slices, you want to look for an eggplant that is relatively similar in size all along its length. Otherwise, you might end up with small rounds and much larger rounds.