For the yogurt béchamel sauce
1 bay leaf
1/ 2 medium onion, peeled
2 whole cloves
1 1/2 cups whole milk
1 ½ cups heavy cream
1 1/2 tablespoons unsalted butter
1/2 cup all-purpose flour
Coarse salt and freshly ground black pepper
Freshly grated nutmeg
1/2 cup Greek yogurt* (or 1 cup regular plain yogurt that has been drained for 12 hours in a double thickness of cheesecloth set over a bowl)
For the moussaka
1/ 4 cup dried currants
1 (28-ounce) can whole plum tomatoes
2 1/4 cups olive oil
1 pound 90-percent lean ground beef
1 pound lean ground lamb
Coarse salt and freshly ground black pepper
2 tablespoons ras el hanout* (a Moroccan spice blend), or more to taste
1 teaspoon Aleppo pepper*, or more to taste
About 1 1/2 teaspoons ground cinnamon, or more to taste
4 cups finely diced onion
6 garlic cloves
2 cups dry red wine, such as Agiorgitiko, Cabernet Sauvignon, or Sangiovese
1 pound Idaho potatoes, cut in 18 (1/4-inch) thick slices
2 medium yellow or red bell peppers, cored, seeded, and diced
2 pounds eggplant, cut into 18 (1/4-inch thick) slices
3 cups yogurt béchamel sauce (see above)
1 cup (about 1/ 4 pound) freshly grated kefalotyri* or Parmesan cheese
*Can be found in Middle Eastern markets and specialty shops
To make the yogurt béchamel sauce: Attach the bay leaf to the onion half by piercing it with the 2 cloves. Set aside. Combine the milk and cream in a medium heavy saucepan over medium heat. Cook, without stirring, for 5 minutes, or just until the mixture begins to simmer. Remove from the heat and set aside.
Heat the butter in another medium heavy saucepan over medium heat. When melted and hot, add the flour and cook, stirring constantly, until the mixture is thick and smooth. Cook, stirring constantly, for 10 minutes. Remove from the heat, and whisking constantly to prevent lumps from forming, add the hot milk mixture in a slow, steady stream. When well blended, return the mixture to medium heat. Add the onion half and bring to a simmer. Simmer for 10 minutes. Season with salt, pepper, and nutmeg to taste. Remove from the heat and set aside to cool. When cool, fold in the yogurt and set aside until ready to use. You will have 4 cups. Reserve any leftover for another use.
To make the moussaka: In a small bowl, pour hot water to cover over the currants and let soak for 30 minutes.
Meanwhile, drain the tomatoes, reserving the juice. Using your hands, crush the tomatoes. Measure out 2 1/2 cups and combine them with the juice. (You will probably have about 1/ 2 cup tomatoes left over.) Set the tomatoes aside.
Place a large skillet over medium heat. When very hot but not smoking, add 2 tablespoons of the olive oil, swirling to coat the pan. Add about a quarter each of the beef and lamb and cook, stirring to break up the meat, for 5 minutes, or until the meat has browned lightly. Season with a generous pinch of salt and pepper and then with 1/ 4 teaspoon each of ras el hanout and Aleppo pepper and a pinch of cinnamon. Using a slotted spoon, transfer the mixture to a colander placed in a mixing bowl.
Return the pan to medium heat and repeat three times to brown and season all the meat. Discard the oil.
Return the skillet to medium heat. Add 1/ 4 cup of the remaining olive oil and, when hot, add the onion along with a pinch of salt. Cover and cook, stirring occasionally, for about 10 minutes, or until the onion is soft and translucent. Add the garlic, stirring to just combine and cook for another minute. Add the wine and cook, stirring occasionally, for about 25 minutes, or until the pan is almost dry. Add the reserved tomatoes along with their juice, stirring to combine. Bring to a simmer. Add the reserved meat mixture, stirring to combine well. (Take care, as the pan will be quite full.) Taste, and if necessary, season with additional ras el hanout, Aleppo pepper, and cinnamon. Lower the heat, and cook at a bare simmer for 6 to 8 minutes.
Drain the currants and stir them into the meat mixture. Taste and, if necessary, season with salt and pepper. Cook for another 30 minutes. Transfer the meat mixture to a mixing bowl set over an ice bath to cool. When cool, set aside.
Place a large sauté pan over medium heat. When hot, add 1/ 2 cup of the remaining olive oil, swirling to coat the pan. When very hot, add the potato slices, 6 at a time, and fry, turning occasionally, for about 15 minutes, or until blond. Transfer to a double layer of paper towel to drain. Repeat the process with the remaining potatoes, adding more oil as needed. When all of the potatoes have been fried, drain off half of the oil in the pan.
Return the pan to medium heat. When hot, add 1/ 4 cup of the remaining olive oil, swirling to coat the pan. When very hot, add the peppers and sauté for about 5 minutes, or until just wilted. Season with salt and pepper to taste and remove from the heat. Transfer to a plate to cool.
Preheat the oven to 500 degrees F.
Combine 1/ 2 cup of the remaining olive oil with salt and pepper to taste in a small bowl. Using a pastry brush, lightly coat both sides of the eggplant slices with the seasoned oil. Then season the slices with additional salt and pepper to taste. Place half of the slices on a baking sheet. Do not crowd the pan. Place in the preheated oven and roast for 6 to 8 minutes, or until lightly charred. Turn and roast for another 8 minutes, or until both sides are equally charred. Transfer to a platter to cool and continue broiling until all the eggplant is well cooked and charred.
If baking the moussaka immediately, lower the oven temperature to 350 degrees F. Place the potato slices in one even layer over the bottom of a 13- by 8- by 2-inch deep rectangular baking dish. Place the eggplant slices, slightly overlapping, in one even layer over the potatoes. Repeat with an even layer of peppers. Spoon the meat mixture over the peppers, spreading it out with a spatula to make an even layer. Top with a thin layer of béchamel and sprinkle with the cheese. At this point the moussaka may be covered with plastic wrap and refrigerated for up to 2 days before baking. Place the moussaka on a baking sheet in the preheated oven and bake for 25 minutes, or until bubbling around the edges. Remove from the oven and let stand for about 10 minutes before serving.