1Prepare the meat sauce: Heat olive oil in a pan over medium heat. Sauté the ground beef until browned. Add the blended onions and garlic, stirring until fragrant. Pour in the cognac or wine and let it simmer for 1–2 minutes. Add the blended tomatoes, tomato juice, cinnamon stick, bay leaf, salt, and pepper. Lower the heat and let the sauce cook for 25 minutes. Stir in the chopped parsley, cook for 1 more minute, and set aside.
2Prepare the vegetables: Slice the potatoes and eggplants into 1/4-inch (6 mm) thick pieces. Fry the potato slices until golden and set aside. Fry the eggplant slices in olive oil until softened and lightly golden. Place them on paper towels to absorb excess oil.
3Make the béchamel sauce: In a saucepan, mix the milk and cornstarch. Stir constantly over medium heat until it thickens. Add the butter, nutmeg, salt, and pepper. Mix well. Remove from heat and whisk in the grated cheese and egg yolks. Set aside.
4Assemble the moussaka: Preheat the oven to 320°F (160°C). Grease a baking dish and sprinkle breadcrumbs evenly on the bottom. Add a layer of grated cheese, then a layer of fried potatoes. Add another layer of grated cheese, followed by a layer of fried eggplants. Sprinkle lightly with salt. Spread the ground beef sauce evenly over the vegetables. Add another layer of potatoes, followed by a final layer of eggplants. Pour the béchamel sauce over the top, spreading it evenly. Sprinkle with grated cheese.
5Bake: Bake in the preheated oven for 50 minutes, or until the top is golden and bubbly.
6Serve: Let the moussaka cool for 1-2 hours before slicing and serving.