Halve the aubergines [eggplants] and hollow out four deep slits, 1/4 inch wide, crosswise in each half, reserving the scooped out flesh.
Sprinkle with 1 teaspoon of the salt and degorge for 30 minutes.
Drain the aubergines [eggplants] and set aside.
Meanwhile, in a large frying pan, melt the butter over moderate heat.
When the foam, subsides, add the onions and garlic and cook them, stirring occasionally, for 5 to 7 minutes, or until they are soft and translucent but not brown.
Add the tomatoes, raisins, reserved aubergine [eggplant] flesh, the remaining salt, the pepper, thyme and parsley.
Reduce the heat to low and simmer the mixture, stirring occasionally, for 10 to 12 minutes, or until it has pulped.
Remove the pan from the heat and allow the mixture to cool.
Preheat the oven to cool 300°F (Gas Mark 2, 150°C).
When the mixture is cool, spoon it into the slits in the reserved aubergine [eggplant] halves.
Spread the remaining mixture over the top of each half.
Place the aubergines [eggplants] in an ovenproof dish large enough to hold them in one layer.
Spoon 1 tablespoon of olive oil over the top of each aubergine [eggplant] half, then pour the remaining oil carefully around them.
The oil should come about one quarter of the way up the sides of the aubergines [eggplants].
Bake the mixture for 1 3/4 hours, or until the aubergines [eggplants] are very soft and there is a slightly sticky residue on the bottom of the dish.
Remove the dish from the oven and cool to room temperature.
Chill the aubergines [eggplants] in the refrigerator for 1 hour, or until they are very cold.
Remove the dish from the refrigerator, carefully transfer the aubergines [eggplants] to a serving dish and serve.