Halve 2 of the eggplants lengthwise, score their pulp deeply with a sharp knife, being careful not to pierce the skins, and with a grapefruit knife scoop out the pulp, reserving it and leaving 1/2-inch-thick shells. Sprinkle the shells with 1 teaspoon salt and invert them on paper towels to drain for 15 to 30 minutes. Cut the reserved pulp and the remaining whole eggplant into 1/2-inch pieces, in a colander toss the pieces with the remaining salt, and let them drain for 15 to 30 minutes.
Pat the shells dry with paper towels, brush them with 1 tablespoon of the oil, and broil them on the rack of a broiler pan, skin side down, under a preheated broiler about 4 inches from the heat until they are tender, about 5 minutes.
In a skillet, heat the remaining 3 tablespoons oil over moderately high heat until it is hot but not smoking. Saute the onion and the garlic until translucent. Add the ground lamb and the eggplant pieces, patted dry, stirring, until meat loses all color and eggplant is tender.
Remove the skillet from the heat, stir in the parsley, mint, tomatoes, feta, and salt and pepper to taste, and divide the filling among the shells, mounding it. Broil the stuffed eggplants in a large flameproof baking dish for 5 minutes, or until the filling is bubbling and golden.
Recipe adapted from Gourmet Magazine