2. Meanwhile, in a saucepan combine sugar, flour, salt, mustard and pepper. Add vinegar and water; bring to a boil. Boil and stir for 2 minutes. Add a small amount from the sauce pan to the eggs; return all to the pan.

3. Cook and stir for 1-1/2 to 2 minutes or until mixture is thickened and a thermometer reads 160 degrees. Refrigerate until cooled.

4. Peel potatoes if desired; slice and place in a large bowl. Add onions. Stir sour cream into dressing; pour over potato mixture and toss to coat.