HOW TO MAKE POTATO SALAD

3 lbs small white potatoes (skins on)
salt to season
1 cup mayonnaise
1/4 cup buttermilk
2 tablespoons Dijon mustard
2 tablespoons whole grain mustard
1/2 cup chopped fresh dill or chopped parsley (if using dill, taste your salad for correct seasoning)
fresh ground black pepper
1/2 cup chopped celery
1/2 cup chopped red onion
1 pinch crushed red pepper flakes (optional