For the salad: Bring a pot of water to a boil. Prepare an ice-water bath. Blanch the green beans until crisp-tender. Immediately transfer to the ice water to stop the cooking process. Repeat with the wax beans. Drain the blanched beans thoroughly.
In a large bowl, combine the green beans, wax beans, blue cheese, cranberries, walnuts, chives and bacon.
For the dressing: In a small bowl, whisk together the Dijon and vinegar until emulsified. Add the shallots. Whisk in the olive oil until emulsified. Season with salt and pepper.
Add the dressing to the salad and toss to coat. Add a few turns of freshly ground black pepper, if desired.