Trim and peel celery root. Cut into very fine julienne strips (about 1" long). You should have 31/2 to 4 cups. Place in bowl of cold water with 3 Tbs. lemon juice to prevent discoloring.
Beat egg yolk with mustard and tomato paste until smooth. Slowly beat in vinegar and both oils. When smooth beat in remaining 3 Tbs. lemon juice, and add salt & pepper to taste.
Drain celery root and pat dry. Toss with dressing and marinate covered at least 2 hrs. in refrigerator. Sprinkle with basil and parsley before serving. Serves 6.
