Lightly brush eggplant halves with oil. Place cut side down on a cookie sheet and bake for 50 to 60 minutes or until flesh feels soft. Allow to cool. When the eggplant has cooled, scoop out flesh, chop coarsely and set aside. Meanwhile, place onion slices in skillet with water, cover and cook over low heat until soft, about 10 minutes. Combine with eggplant, thyme and stock in a 2 quart saucepan. Simmer for 15 minutes. Ladle into soup bowls.