Prepare and Roast the Potatoes
Preheat the oven to 400°F (200°C). Peel and wash the potatoes, then slice them into ¼-inch thick rounds. Lightly oil a baking tray and arrange the potato slices in a single layer.

Prepare and Roast the Eggplant
Peel the skin off the eggplants and slice them into ½-inch thick rounds. Sprinkle them with salt and let them rest for 20 minutes to draw out excess moisture. Rinse each piece, pat them dry, and arrange them on a lightly oiled baking tray—you may need two trays, depending on the quantity. Drizzle with olive oil and bake at 400°F (200°C) for about 30 minutes, flipping both the eggplant and potatoes halfway through. Once tender and golden, remove from the oven and set aside.

Cook the Spiced Ground Beef Filling
Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Add the ground beef and break it apart with a wooden spoon to prevent clumps. Cook for 10 minutes, then stir in the onion and continue cooking for another 5 minutes until softened. Add the minced garlic, nutmeg, and cinnamon, mixing well to infuse the flavors. Finally, stir in the tomato paste until fully combined, coating the meat mixture evenly.

Add Tomatoes and Simmer the Meat Sauce
Add a splash of red wine to the pan, letting it sizzle and reduce for a richer flavor. Stir in the crushed tomatoes for added depth, followed by a teaspoon of sugar to balance the acidity. Lower the heat and let the mixture simmer for 30 minutes, stirring every 5 minutes to prevent sticking. Season with salt and pepper to taste, then turn off the heat and set aside until ready to use.

Make the Creamy Béchamel Sauce
In a medium saucepan, melt the butter over medium heat, then whisk in the flour until smooth and well combined. Gradually pour in the milk, whisking constantly to prevent lumps, until the mixture thickens into a creamy consistency. Stir in the cheese and egg yolk, mixing until fully incorporated. Season with salt, pepper, and a pinch of nutmeg for a rich, savory flavor. Remove from heat and set aside.

Layer the Moussaka in a Baking Dish
Use a 13x9-inch baking dish that’s at least 3 inches deep. Start by arranging the cooked potatoes in an even layer on the bottom, followed by a layer of roasted eggplant. Spread the meat mixture evenly over the top, ensuring it fully covers the layers for a well-balanced bite in every slice.

Finish with Béchamel and Cheese
Sprinkle ¼ cup of shredded Parmigiano Reggiano over the meat mixture, then add another layer of eggplant on top. Pour the béchamel sauce evenly over the entire dish, ensuring full coverage for a creamy, golden finish. Finally, sprinkle a light dusting of nutmeg for extra warmth and depth of flavor.

Bake, Rest, and Serve
Bake at 375°F (190°C) for 40 minutes or until the top is golden and caramelized. Remove from the oven and let it cool for 15 minutes to help the layers set before slicing into portions. Garnish each serving with chopped parsley for a fresh touch, and enjoy!