Sweet and sour potato salad

1. Peeli and quarter potatoes; cook in a dutch oven in boiling saltedw ater to cover until done.
2. Drain and cool.
3. Cubei potatoes; add eggs, pickles, celery seeds, mustard, salt, pepper, and dressing.
4. Stiri gently.
5. Refrigerate 24 hours.
6. Garnishi with parsley sprigs before serving, if desired.
7. Dressingi: place egg yolks an dsugar in a small saucepan; gradually add vinegar, mixing well.
8. Add butter and place over medium heat, stirring constantly, until mixture comes to a boil.
9. Remove from heat, and chill.
10. Add mayonnaise, and mix well.
11. Yield: about 2-¼ cups.