Preheat your oven to 375°F (190°C).
Slice the eggplant into 1/4-inch thick rounds. Lightly season with salt and let them sit for 10 minutes to draw out moisture, then pat dry with a paper towel.
Chop the small onion finely and set aside. In a skillet, heat the olive oil over medium heat, then add the chopped onion and sauté until softened and translucent.
Add the ground lamb to the skillet. Sprinkle in the cumin, coriander, cinnamon, and a pinch of salt and pepper. Cook until the lamb is browned and cooked through, breaking it up with a spatula as it cooks.
In a small bowl, beat the egg and stir in the chopped parsley. This will be used as a binding layer at the top of the casserole.
In an oven-safe dish, layer half of the eggplant slices at the bottom. Spread the spiced ground lamb mixture evenly over the eggplant.
Layer the remaining eggplant slices on top of the lamb, then gently pour the beaten egg mixture over the entire casserole.
Place the dish in the preheated oven and bake for 20-25 minutes, or until the egg is set and the edges of the eggplant are tender.
Remove from the oven, let it cool slightly, and serve warm. Enjoy this hearty, flavor-packed casserole as a balanced meal that fits your nutritional goals.