Grilled pear and watercress salad

1 tablespoon water

2 tablespoons chopped walnut s

2 firm yet ripe pear s, cored and cut into 6 lengthwise wedges, peel intact

Lemon juice for brushing

For the vinaigrette

2 tablespoons fresh lemon juice, plus extra for brushing

1 tablespoon rice vinegar

1 teaspoon Dijon mustard

1 tablespoon minced shallot

1/4 teaspoon salt

1/4 teaspoon freshly ground black pepper

1 tablespoon extra-virgin olive oil

6 cups watercress sprigs, tough stems removed

3 tablespoons crumbled blue cheese