Submerge the onion slices in a bowl of ice water for 30 minutes to mellow the flavor. Drain and pat dry with paper towels.
Meanwhile, in a pot of boiling, salted water, cook the green beans until crisp-tender, about 2 minutes; drain and rinse under cold water until cool. Pat dry with paper towels.
In a small jar or plastic container with a tight-fitting lid, combine the EVOO, lemon juice, chives, sugar, 1 tsp. salt and 1/2 tsp. pepper. Cover tightly and shake vigorously to blend.
In a large bowl, toss the green beans and onion with the dressing; transfer to a large serving bowl or platter. Top with the pine nuts and parmesan. Serve immediately or let sit for up to 3 hours.