Roast the eggplants
30 minPrick the eggplants in several places with a fork and place them directly over a stovetop flame or on a grill grate; without the holes, steam can build up inside and burst the skin. Use tongs to turn them until every side is blackened; the skin should blister and the eggplant should collapse in on itself. Each eggplant takes 10–12 minutes. If you roast two at a time over a stove flame, five will take 30 minutes. A fork inserted into the thickest part should meet no resistance, which means the inside has softened completely. Partly undercooked eggplant can leave lumps in the béchamel.