How to Make It
In a saucepan of boiling salted water, cook the onions until just tender, about 4 minutes. Drain and let cool, then peel.
In a bowl, mix the oil with the vinegar; season with salt and pepper. In a large salad bowl, toss the lettuces with the onions, chives, tarragon and basil. Add the vinaigrette, toss to coat and serve.