Mashed Potato Salad

1-1/2 pounds red potatoes (about 5 small potatoes), scrubbed but unpeeled, cut into chunks
1-1/2 pounds white potatoes (about 5 small potatoes), peeled, cut into chunks
1 tsp white vinegar
3/4 cup mayonnaise
2 Tablespoons prepared mustard
1/4 cup sour cream
1 rib celery, diced (* optional)
1 cup finely-diced red onion (* optional)

Boil potatoes until soft, about 20 minutes
Strain potatoes and sprinkle with vinegar, shaking to coat
Put together dressing while potatoes cool: mayo, mustard, and sour cream
Add dressing after cooled a bit, 10 minutes or so
Mash while you are adding dressing to your desired consistency
Add “chunky bits” if you like them, celery and red onion
Chill before serving

* I have not tried this recipe with the celery and red onion but I have made potato salad in the past. Adding these will give it a more traditional potato salad crunch as opposed to a smooth mashed potato feel. I always pour boiling water over the onions after dicing to get rid of the onion aftertaste if I am using raw.