How to Make It
In a large saucepan, cover the drained cannellini beans with 2 inches of water. Add the yellow onion, carrot and celery and bring to a boil. Simmer over low heat, stirring occasionally, until the cannellinis are tender, about 1 hour and 15 minutes. Drain the cannellinis and discard the onion, carrot and celery.
Meanwhile, bring a large saucepan of salted water to a boil. Fill a large bowl with ice water. Add the wax beans to the saucepan and cook until just tender, 3 minutes. Drain the beans and chill them quickly in the ice water. Drain and pat dry.
In a small bowl, combine the olive oil with the vinegar and lemon juice and season with salt and black pepper.
In a large bowl, toss the cannellini beans with the wax beans, radishes, red onion and basil. Add the vinaigrette and toss to coat. Season with salt and black pepper and serve right away.