How to Make It
Preheat oven to 400ºF. Line a baking sheet with heavy-duty foil. Place eggplants on sheet, cut sides up. Combine 2 Tbsp. oil and garlic; brush over eggplants. Sprinkle with salt. Bake until golden and tender, about 30 minutes, depending on size.
Bring 1 cup water to a boil in a medium saucepan. Add couscous, cover, and turn off heat. Let stand 5 minutes. Fluff with a fork, then stir in mint, lemon zest and juice; fluff again. Season with salt.
Scoop eggplant flesh from skins, leaving about 1/2 inch behind. Chop flesh and toss with couscous mixture and remaining 2 Tbsp. oil. Season with salt.
Set oven rack about 3 inches from heating element and preheat broiler to high. Pile couscous mixture in eggplant shells, sprinkle with feta and broil until cheese begins to brown, 1 to 1 1/2 minutes.