Roast your eggplants on the grill, and remove the pulp. Once you've extracted the flesh and discarded the skin and seeds, use it right away. If not, let the pulp sit in a bowl with some water and lemon juice in it. This prevents the eggplant from darkening.
Put your eggplant into a fine wire strainer, and squeeze out any excess liquid. Transfer the pulp to a mixing bowl.
Add the olive oil, salt, pepper, and optional crushed garlic or onion.
With a fork, whip the mixture until it becomes homogeneus, light, and fluffy with no large chunks or strings of eggplant. This can take awhile. You may have to take several breaks in between to rest your arm.
Once the puree is ready, you can gently stir in your optional mayonnaise. Chill before serving.
The traditional way to eat eggplant salad is straight up as an appetizer or salad. It's also delicious spread on crunchy crackers, or toasted bread.