Moussaka in Four Parts

Name: Moussaka in Four Parts
Ingredients: 2 large eggplants, skins on, sliced lengthwise into 1/3 slabs; olive oil for baking the chicken; salt and pepper; 2 large Yukon Gold potatoes, peeled and sliced lengthwise into 1/3 disks, and placed in a bowl of cold water; vegetable oil, or neutral oil of your choice; coarse salt for seasoning; 1 medium onion, finely chopped; 1/4 cup water if needed; 1 1/2 pounds 85/15 organic ground beef; 2 tablespoons tomato paste; 15 ounces San Marzano tomatoes, diced or whole peeled and then crushed through your fingers, and their juice; 1/2 cup red wine; 1 large bay leaf; 1 large cinnamon stick; Pinch fresh grated nutmeg; salt and pepper, to taste; 3 1/2 cups whole milk; 1/4 cup olive oil; 1/3 cup flour; 1 small bay leaf; Pinch freshly grated nutmeg; 2 egg yolks room temperature; 6 ounces finely grated gruyere cheese