Preheat the oven to 450 degrees. Trim the eggplants and cut lengthwise into 1/2-inch-thick slices. Arrange on 2 large foil-lined baking sheets; brush generously with 1/2 cup olive oil and season with salt and pepper. Bake until soft, about 30 minutes.
Heat the remaining 2 tablespoons olive oil in a Dutch oven or heavy pot over medium-high heat; add the chard and season with salt and pepper. Cook, stirring, until wilted, about 4 minutes. Transfer to a colander and let cool; squeeze out excess moisture and set aside.
Wipe the pot dry; add the butter and melt over medium-high heat. Add the onion; cook until golden, about 4 minutes. Add the garlic and cook 1 more minute. Add the lamb, breaking it up into pieces, with the oregano, cinnamon, nutmeg, 2 teaspoons salt and pepper to taste; cook until the meat is slightly browned, about 2 minutes. Add the wine and cook, stirring, until the meat is cooked but still slightly pink, 1 more minute. Add the diced tomatoes, tomato paste, Worcestershire sauce and bay leaves; bring to a simmer, cover and cook for 30 minutes.
Meanwhile, lightly oil a 9-by-11-inch casserole dish and sprinkle with the breadcrumbs. Place the potato slices in the dish; pat dry with paper towels and season with salt and pepper.
As the sauce continues to cook, make the cheese custard: Melt the butter over medium heat. Whisk in the flour, cooking slightly to form a soft paste. Off the heat, whisk in the milk, nutmeg and 2 teaspoons salt. Return to the heat and bring to a boil, whisking. Remove from the heat again; stir in 1 cup cheese, cool slightly, then whisk in the eggs and egg yolks.
Reduce the oven to 350 degrees. Layer half of the eggplant on top of the potatoes. Cover with half of the meat sauce, then half of the chard. Repeat with the remaining eggplant, meat sauce and chard. Pour the custard sauce on top, then sprinkle with the remaining 1/2 cup kefalotiri cheese. Bake the moussaka, uncovered, until the custard is set and lightly browned, about 1 hour. Let rest 20 minutes before serving.