Cut the base off the frizzy endive and wash the leaves well; dry in a salad spinner and leave while you prepare the other ingredients. Make the vinaigrette in the usual way, adding a small quantity of walnut oil – too much can be a bit overwhelming. To make the salad, tear the leaves into manageable pieces and place in a salad bowl with the onion and half the walnuts. Toss well with the vinaigrette. Put the salad on serving plates and top with the cheese. Sprinkle on the remaining walnuts and a scattering of chives. Serve with country bread.