1) Preheat oven to 180C/Gas 3.
2) Spread the nuts on a baking tray in a single layer. Bake, shaking the tray occasionally, until the nuts are toasted and fragrant, about 7 to 10 minutes. Let the nuts cool, and then coarsely chop.
2) Trim the stems of the watercress and rocket. Wash and dry the leaves.
3) Meanwhile, whisk the vinegar and mustard together in a large salad bowl. Season with the 1/4 tsp salt and some pepper. Gradually whisk in the olive oil, starting with a few drops and then adding the rest in a steady stream, to make a smooth, slightly thick dressing.
4) Halve the chicory lengthwise, cut out core, then thinly slice crosswise and add all the lettuces to the bowl. Quarter and core the unpeeled pears and thinly slice; add to the salad. Scatter the cheese and nuts over the salad, and season with salt and pepper, to taste. Toss the salad gently to evenly dress all the greens.
5) Divide among 4 plates and serve immediately.