Pre-heat oven to 400 degrees F/200 degrees C. Slice the eggplants in halve lengthwise, leaving the stems intact. Score a cross hatch pattern into each eggplant halve. Place the prepared eggplants flesh side up in a baking dish. Drizzle the eggplants with olive oil and season with salt. Roast for 35-40 minutes, until tops are deep golden and flesh is soft.
While the eggplants roast, add 2 tablespoon olive oil to a skillet set over medium heat, add onion & sauté for 6-8 minutes, until softened. Add ground lamb, finely chopped prunes, salt, oregano, cinnamon & smoked paprika and cook for 10 minutes, stirring often. Add in tomatoes, tomato paste and 1 tablespoon balsamic vinegar. Cook for another 10 minutes, adjust seasoning with salt if needed. Set lamb sauce aside while you finish preparing the eggplant & béchamel. (The USDA recommends ground lamb reach an internal temp of 160F)
Remove the eggplant from the oven after 35-40 minutes and use a spoon to press down the centers of the now softened eggplant halves. Fill eggplants with lamb sauce.
For the béchamel: melt butter in a small saucepan over medium heat. Add flour and cook, stirring constantly for 3 minutes until the flour smells slightly nutty. Gradually add in the milk, stirring constantly and cook for 10-12 minutes until mixture starts to thicken. Stir in egg yolks, salt, nutmeg and grated kefalotyri and continue to cook, stirring often for another 10 minutes until nice and thick.
Pre-heat the broiler to 425 degrees F. Divide lamb mixture amongst the eggplant halves. Top with béchamel and a bit of finely grated Kefalotyri cheese*. Broil for 5 minutes or until golden brown. Garnish with fresh oregano leaves to serve and enjoy!
*Kefalotyri substitutes: Gruyere, Pecorino or Romano
The USDA recommends ground lamb reach an internal temp of 160F.