Choose rather thin and long eggplants, color should be dark. Cut the green part short but keep the stem. Grill them until softened, make sure they don't burn. Turn from time to time so that each side is grilled. Cooking time might vary. Another option is to bake them in the oven, but make sure to sting them with a toothpick before. 40 minutes on 190° should be enough.
Peel the eggplants while still hot and make sure no peel pieces are left as these can be bitter. Use a pliers.
Cut lengthwise and let the juices drip for a while (few hours or even overnight in a cool place).
2 ggplants should be more than enough for 2 persons. I prefer to prepare more and at this point freeze some. Mash the rest on the cutting board by cutting it with a big knife. I prefer to avoid the food processor because mincing the seeds would influence the taste.
Mix the eggplants mash with mayo - preferably home-made. Season with salt. Add finely chopped onion if you prefer. Or choose the vegan variant by simply replacing the mayo with sunflower oil and mixing it with the eggplants and onion.