1/3 c. cider vinegar
2 tbsp. vegetable oil
1 lg. egg
1 tbsp. sugar
1/2 tsp. salt
1/2 tsp. celery seed
1/2 tsp. dry mustard
1/4 tsp. pepper

Put all ingredients in top of double boiler. Beat with whisk or wooden spoon until well blended. Place over simmering water and cook, beating constantly, about 4 minutes until thickened. Transfer to a bowl, cool, cover and refrigerate until well chilled. Keeps well.