Preheat the oven to 400 degrees F (200 degrees C).
Wipe the eggplants and cut them in half lengthwise. Pour a thin layer of olive oil into a baking pan and place the eggplants, cut side down, in the oil. Bake until soft and squishy, about forty minutes.
To make the cucumber yogurt, wipe the cucumber half and grate coarsely. Sprinkle lightly with salt and set aside in a colander for half an hour. Squeeze the cucumber dry in the palm of your hand, then stir it into the yogurt.
Peel and finely crush the garlic, chop the mint leaves, and stir both into the cucumber and yogurt.
Toast the black onion seeds lightly in a nonstick pan.
Transfer the yogurt to a serving bowl and sprinkle with the onion seeds.
Serve the eggplants on plates with the cucumber yogurt. Spread some of the baked eggplant onto a piece of the bread, spoon over a little of the yogurt, and eat.
Reprinted with permission from Tender: A Cook and His Vegetable Patch by Nigel Slater, copyright (c) 2009. Published by Ten Speed Press, a division of Random House, Inc.