1. Thinly slice apple wedges in a food processor fitted with a slicing blade. Combine apples, lemon juice, and sugar in a large bowl; toss to coat. Slice beet and onion wedges in food processor fitted with a slicing blade; add beet mixture and parsley to apple mixture. Sprinkle with salt and pepper. Stir in oil and mustard; toss gently to coat. Arrange about 2/3 cup salad on each of 8 plates; top each serving with 1 tablespoon walnuts and about 1 1/2 teaspoons cheese.
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