Makes 4 appetizer-size portions
1 pound thin Italian or Asian eggplants (2 to 3), cut into 1/4-inch-thick rounds
5 tablespoons extra-virgin olive oil, divided
2 tablespoons red-wine vinegar
1/4 cup chopped mint
2 tablespoons small capers, rinsed
Preheat broiler. Arrange eggplant in 1 layer on a large baking sheet and brush both sides with 2 tablespoons oil (total). Broil about 4 inches from heat, turning once, until golden, 8 to 12 minutes total.
Stir together vinegar, mint, capers, 1/4 teaspoon salt, 1/2 teaspoon pepper, and remaining 3 tablespoons oil and toss with warm eggplant. Marinate at least 20 minutes.
Marinated eggplant can be made 1 day ahead and chilled. Bring to room temperature before serving.