Blanch the green beans in a large pot of boiling salted water until tender-crisp, 3 minutes. Remove the green beans from the boiling water, run under cold water for a few minutes to stop the cooking, and then drain and dry well.
Whisk together the walnut oil, vinegar and Dijon mustard in a small bowl. Stir in the salt and pepper.
Add the cool green beans to a large bowl and toss in the walnuts, cranberries and shallots and drizzle in the vinaigrette. Place on a platter or serving dish and sprinkle with the blue cheese.