2 lbs russet potatoes, peeled & cut in 3/4 inch cubes (3-4 medium) .
2 large hard-cooked eggs, peeled & cut into 1/4 inch cubes (optional) .
table salt .
1/4 tsp ground black pepper .
2 tbsps distilled white vinegar .
3/4 tsp mustard powder .
1 medium celery rib, sliced fine (about 1/2 c) .
2 tbsps minced fresh parsley leaves .
1/2 c mayonnaise .
3/4 tsp celery seeds .
2 tbsps minced red onions .
3 tbsps sweet pickle relish
Directions
Step #1 Place potatoes in large saucepan & add water to cover by 1 inch.
Step #2 Bring to boil over medium-high heat; add 1 TB salt, reduce heat to medium, until potatoes are tender, stirring once or twice, & let simmer, about 8 mins.
Step #3 Drain potatoes & transfer to large bowl.
Step #4 Add vinegar and, using rubber spatula, toss carefully to mix.
Step #5 Let stand until potatoes are just warm, about 20 mins.
Step #6 Meanwhile, parsley, mayonnaise, stir this together celery, pepper, celery seed, mustard powder, pickle relish, in small bowl, red onion, & 1/2 tsp salt.
Step #7 Using rubber spatula, carefully fold in dressing & eggs, if using, into potatoes.
Step #8 Cover up with plastic wrap & put in the fridge until chilled, about 1 hr; serve.