To prepare the vinaigrette, place the first 7 ingredients in a medium bowl; stir well with a whisk.
To prepare the salad, divide the lettuce leaves evenly among 6 salad plates. Toss pear with 2 tablespoons orange juice. Divide pear and onion evenly among leaves. Top each serving with about 1 tablespoon cheese and 1 teaspoon walnuts. Drizzle each serving with about 2 1/2 tablespoons vinaigrette.