Prepare the Eggplant: Preheat your broiler to a medium setting.
Peel the eggplants and slice them lengthwise into ⅓-inch / 0. 8 cm thick planks.
Cut each plank into 2 or 3 long strips.
Arrange the eggplant strips in a single layer on baking sheets.
Brush one side generously with olive oil and sprinkle lightly with salt. Broil for 7-10 minutes, until the tops begin to turn a beautiful golden brown. Carefully flip the strips, brush the other side with olive oil and salt, and broil again until golden.
Create the Savory Sauce: While the eggplant broils, heat ⅓ cup / 80 ml (2.7 fl oz) of olive oil in a large skillet or pot over medium heat.
Add the chopped onions and sauté until they become soft and translucent, about 5-7 minutes.
Stir in the minced garlic and cook for another minute until fragrant.
Add the tomato wedges, cooked spinach, chives, and celery leaves.
Let the mixture simmer for 10 minutes, allowing the flavors to meld.
Season and Assemble: Stir the dried oregano, black pepper, and fresh lemon juice into the sauce.
Season with salt to your liking.
Spread a few spoonfuls of the sauce on the bottom of a large, fireproof casserole dish.
Arrange one-third of the broiled eggplant strips over the sauce.
Continue layering the sauce and eggplant, finishing with a final, generous layer of sauce on top.
Simmer to Perfection: Cover the casserole with a tight-fitting lid and place it over a medium flame on the stovetop.
Simmer for 10 minutes to allow the flavors to marry completely.
Toast the Garnish and Serve: While the casserole simmers, spread the sesame seeds on a small baking sheet. Toast in a 350°F / 175°C oven for 3-5 minutes, stirring occasionally, until they are fragrant and golden brown. Watch them closely as they can burn quickly!
Sprinkle the toasted sesame seeds over the finished casserole just before serving hot.