For the meat sauce:

1. In a large heavy-bottomed pot such as a Le Creuset Dutch oven, brown the lamb. Add the onions and garlic and cook until the onions are soft. Add the chopped tomatoes, tomato paste, red wine, lemon juice and zest, spices, herbs, salt and pepper. Stir to combine and simmer on medium-low for about 40 minutes. Adjust seasoning and set aside. 
2. While the meat sauce is cooking prepare the eggplant and potatoes.

For the eggplant:

1. Heat oven to 450 degrees. Slice the eggplant in 1/4″ slices. Brush slices on both sides with olive oil and layout on a baking sheet. Roast for about 20 minutes, flipping after 10 minutes, until eggplant is soft and starts to take on some color. Don’t overcook. Remove from oven and set aside. 

For the potatoes:

1. Peel the potatoes and slice in 1/4″ disks. Brush with olive oil and season with kosher salt and fresh ground pepper. Roast for 12 – 15 minutes, flipping after about 7 minutes, until the potatoes are cooked al dente and beginning to take on a little color. Don’t overcook. Remove from oven and set aside.

For the béchamel sauce: 

1. Scald the milk in a pot, so the milk around the edges of the pan just begins to bubble. Do not let the milk come to a boil. 
2. Melt the butter in a large skillet over medium heat. When butter is hot, whisk in the flour a couple tablespoons at a time, whisking continually. The mixture will form a paste. Cook a minute or two, but do not let the mixture brown. Add the hot milk slowly while continuing to whisk constantly until all the milk is incorporated and the sauce is smooth and thick. Cook a minute or two and season with nutmeg, salt and pepper. 
3. Remove from the heat and whisk in three egg yolks. Using an electric mixer, beat the egg whites to firm peaks and then fold into the béchamel sauce. Set aside.

To assemble the moussaka:

1. Heat oven to 350 degrees. Rub a large a large ceramic or glass casserole dish with a thin coat of olive oil or butter. I use a 13 1/2 ” x 12″ x 3″ ceramic dish. A 13″ x 9″ x 2″ will be a little small. Alternatively, you can cook in two smaller bakers.
2. Place the potatoes in the bottom of the casserole dish in a single layer. Put half of the eggplant slices on top of the potatoes and top with half of the meat sauce. Sprinkle with 1/3 of the parmesan cheese. Layer on the remaining eggplant slices and cover with the remaining meat sauce. Sprinkle on 1/3 of the parmesan cheese.
3. Cover the entire casserole with the béchamel sauce and sprinkle on the remaining parmesan cheese. Bake for 30 to 40 minutes until the top of the moussaka is golden brown. Remove from the oven and allow to rest 20 minutes before serving. Cut into squares and serve.