Preheat oven to 350°F. In large sauté pan, melt 1 tablespoon butter over medium heat. Add lamb, breaking up with spoon and brown. Add onion and sauté until translucent, about 5 minutes. Add garlic and cook until fragrant, about 1 minute.
Add diced eggplant, cinnamon, allspice and salt, tossing with lamb to combine. Cover and cook until eggplant is tender, about 10 minutes.
Add tomato paste to lamb mixture and stir to combine. Then incorporate wine, parsley and crushed tomatoes. Allow sauce to simmer, uncovered, 10-15 minutes, until excess liquid evaporates. Season to taste with salt and pepper.
Cook pasta according to package directions, just until al dente. Drain, rinse with cold water and toss with egg whites and fontina cheese. Set aside
While pasta is cooking, make béchamel sauce by melting 8 tablespoons (1 stick) butter in 2-quart saucepan over medium heat. Add flour and cook, whisking constantly, until pale and smooth, 2 minutes. Whisking constantly, add milk in steady stream until incorporated. Add bay leaf and cook, whisking often, 10-15 minutes. Season with salt, pepper, and nutmeg and discard bay leaf. Let sauce cool 5 minutes. In small bowl, whisk together yogurt and egg yolks and whisk into sauce until smooth; set aside.
Layer half pasta mixture into bottom of large, deep baking pan (10”x15”, holds 4-5 quarts). Sprinkle with three tablespoons Wisconsin feta cheese. Add eggplant and meat filling, spreading over top. Sprinkle with half remaining Wisconsin feta cheese. Top with remaining pasta and remaining Wisconsin feta.
Place baking pan on half-sheet pan (to catch drips) or sheet of aluminum foil and bake 60 to 75 minutes, or until casserole is heated through and béchamel sauce is golden brown. Allow macaroni and cheese to cool 15 – 20 minutes before slicing and serving.
Pour béchamel sauce over macaroni and cheese, allowing sauce to fill in sides and corners of pan.