This sweet-and-tart eggplant appetizer can be frozen for up to three months.
Sauté eggplants in 1/4 cup hot oil in a Dutch oven over medium-high heat for 10 minutes or until tender and slightly brown. Remove eggplant, and set aside.
Sauté onions in 2 tablespoons olive oil in Dutch oven over medium heat 5 minutes or until golden. Add tomatoes and celery; simmer, stirring occasionally, 15 minutes or until celery is tender. Stir in olives, capers, and pine nuts. Return eggplant to Dutch oven.
Stir red wine vinegar, sugar, salt, and pepper into eggplant mixture. Cover and simmer, stirring occasionally, 30 minutes. Cool. Cover and chill 8 hours. Remove from refrigerator 30 minutes before serving. Serve with pita chips or toasted bread rounds.