Step 1Cook the onions in the oil in a 2-quart covered saucepan over medium-low heat, stirring occasionally, until tender but not brown--6 to 8 minutes. Stir in the tomatoes; cover and cook slowly several minutes until they have softened slightly. Stir in the thyme, bay leaf, garlic, saffron and orange peel, if using; salt and pepper lightly to taste. Simmer slowly, partially covered, for 30 minutes, adding a little juice from the tomatoes if the sauce becomes too thick. Taste carefully and correct the seasoning. Makes 2 1/2 cups.
Step 1Steam the eggplants until tender, 40 to 45 minutes, depending on size. They are done when soft and somewhat shriveled; a skewer will pierce through one easily.
Step 2Slice off the caps of the eggplants. Quarter them lengthwise--the flesh should be soft and white. Scoop off all but 1/8 inch of flesh, leaving the skin intact. Coarsely chop the flesh; reserve the skin.
Step 3Set a large skillet over moderate heat, add a little olive oil and cook the onions until tender, 5 minutes. Fold in the garlic and cook a few seconds; blend in the eggplant flesh. Season with salt and pepper, cover the pan and cook slowly 10 minutes, stirring occasionally, until the eggplants are thoroughly tender. Break up the eggplant flesh with a wooden spoon so that there are no large chunks. Uncover, raise the heat and saute for several minutes, tossing to brown very lightly. Fold in the parsley; taste and correct seasoning.
Step 4Meanwhile, oil another large nonstick skillet and brush the eggplant skin with oil. Lay the skin flesh side down in the skillet and set a lid or pie plate on top to flatten it. (You may not need all the skin.) Cook slowly until the skin is tender but not browned, 5 to 10 minutes. Cut the skin into strips and arrange skin side down in an oiled 2 1/2-quart baking dish.
Step 5Melt the butter in a 2 1/2-quart saucepan, then blend in the flour to make a smooth paste. Stir over moderate heat until the butter and flour foam together for 2 minutes without coloring more than a buttery yellow. Remove from the heat.
Step 6When the bubbling stops, pour in all but 1/2 cup of the hot milk, whisking vigorously to blend. Then whisk rather slowly over medium heat, reaching all over the bottom and sides of the pan, until the sauce comes to a simmer. Simmer 2 to 3 minutes, stirring and thinning out the sauce as necessary with dribbles of the milk.
Step 7Beat the egg yolks into the white sauce, then fold in the cooked eggplant flesh, salt and pepper to taste and the grated cheese.
Step 8Heat the oven to 400 degrees and place a roasting pan with 1 inch of water on a rack in the lower middle level. Beat the egg whites until stiff but not dry, about 3 minutes. Stir a quarter of them into the eggplant mixture; delicately fold in the rest. Being careful not to disturb the eggplant skins, turn the souffle mixture into the baking dish. Attach a double-thick strip of oiled aluminum foil around the top of the dish, letting it come 2 inches above the rim but no more than 1 inch below the rim--or it might siphon up the water in the pan.
Step 9Set the souffle in the pan of water;bake until it has puffed and is browned lightly, 1 1/4 hours.
Step 10Remove the souffle from the oven and cool 15 minutes--it will sink an inch or so. Remove the collar and turn a serving platter upside-down over the dish; reverse the two to unmold the souffle. You may wish to decorate the top with tomato cutouts and parsley. Pass the tomato sauce separately. Serve hot, tepid or cold.