How to Make It
Preheat oven to 400°F. Cut each eggplant in half lengthwise through stem. Cut eggplant flesh lengthwise in 3/4-inch intervals, cutting almost to, but not through, the skin. Cut eggplant flesh crosswise in 3/4-inch intervals, cutting almost to, but not through, the skin. Drizzle eggplant flesh evenly with 1 1/2 tablespoons of the oil, and sprinkle evenly with 3/4 teaspoon of the salt. Place eggplant halves, cut sides down, on a parchment paper-lined baking sheet. Roast in preheated oven until tender and lightly browned, about 30 minutes.
Remove from the oven, and cool 10 minutes. Scoop out eggplant flesh, leaving a 1/2-inch-thick border. Chop eggplant flesh, and set aside.
Stir together yogurt, lemon juice, and 1/4 teaspoon of the salt in a small bowl. Cover and chill until ready to use.
Heat remaining 1/2 tablespoon oil in a large skillet over medium-high. Add lamb, and cook, stirring occasionally, until browned and cooked through, 8 to 10 minutes. Transfer lamb to a medium bowl. Add onion to skillet, and cook, stirring occasionally, until tender, 4 to 5 minutes. Add paprika, cumin, coriander, and cinnamon to onion, and cook, stirring constantly, until fragrant, about 30 seconds. Remove from heat. Add onion mixture, eggplant flesh, rice, 1 tablespoon of the mint, and remaining 1/2 teaspoon salt to lamb. Stir just until combined. Divide mixture evenly among eggplant skins, and return to prepared baking sheet. Bake at 400°F until eggplant is browned and filling sets, 15 to 20 minutes.
Drizzle eggplant halves with yogurt sauce, and sprinkle evenly with pistachios and remaining 1 tablespoon mint.