1. Preheat oven to 375F.
2. Cut eggplants in half lengthwise. Using a grapefruit spoon, gently scoop out pulp from eggplant halves, leaving ½” thick shells. Roughly chop the scooped-out pulp and set aside. Sprinkle inside surfaces of eggplant shells with salt, and place face down on a paper towel to drain for 15-30 minutes.
3. Heat 3 tbsp of the oil in a large saute pan over medium-high heat.
4. Add onion and saute until soft, about 5 minutes.
5. Add garlic and red pepper, and continue sauteeing until onion is golden and peppers are soft, about 5 minutes.
6. Add the ground lamb and chopped eggplant, and cook until lamb is browned and eggplant is tender, about 10 minutes. Stir in the tomato paste, cinnamon and red pepper flakes, stirring until just warmed through.
7. Remove from heat. Season to taste with salt and lots of black pepper, then stir in the tomatoes, pine nuts and fresh mint.Pat the shells dry with paper towels, removing any excess salt remaining on the surface.
8. Brush with remaining 1 tbsp oil and arrange in a baking dish, cut side up. Divide the lamb mixture among the eggplant shells, mounding the filling slightly, the top with crumbled feta cheese.
9. Bake in preheated oven for 25-30 minutes, or until the eggplant shells are tender and filling is bubbling and golden.