Iceberg Wedges With Blue Cheese Dressing

Name: Iceberg Wedges With Blue Cheese Dressing
Ingredients: 1 cup crumbled Roquefort cheese; 2/3 cup sour cream; 2/3 cup mayonnaise; 1/4 cup fresh lemon juice; 2 scallions, minced; 1/2 teaspoon chopped thyme; 1/2 teaspoon finely grated lemon zest; 1 tablespoon plus 2 teaspoons chopped flat-leaf parsley; Salt and freshly ground pepper; 6 large wedges of iceberg lettuce (1 1/2 heads); 6 radishes, very thinly sliced