Here's a classic salad that deserves a revival. As is often the case with French salads, the leaves are not meant to be the bulk of the salad (as the lettuce in American salads often is). Rather, the endive provides a pleasantly bitter, nicely crisp backdrop to the cheese and nuts, which are the true stars.
In a large bowl, whisk together the walnut oil and lemon juice. Season with salt and pepper, to taste. Separate the endive leaves, rinse under cold water, and drain well.
Thinly slice the leaves crosswise and add to the bowl of dressing, tossing to coat. Add the walnuts and blue cheese and toss gently. Arrange the salad on 4 salad plates and serve.