Drain the chickpeas in a colander. Peel the onions and cut into fine rings, wash the tomatoes and cut in half. Drain the mozzarella and cut into slices or pluck.
For the dressing, wash the chives, shake dry, cut into fine rolls. Mix together lemon juice, vinegar, salt, pepper, about 1/2 teaspoon sugar and pesto. Fold in the oil and stir in the chives.
Mix the chickpeas, onions, tomatoes and vinaigrette (preferably with your hands). Serve with the mozzarella.