American potato salad - Radagast's SO's style

While I'm on the topic of potato salad, I might as well post a traditional American potato salad recipe. My SO prefers a relatively basic American potato salad, and since we had some extra potatoes last night after making our German potato salad, we also made a batch of my SO's favorite (very oniony) potato salad. Radagast even enjoys it despite it lacking hard-boiled eggs and pickles. This recipe is this week's second end-of-the-week recipe blogging post.

3 pounds potatoes, whole, with skins
1 1/2 cups mayonnaise
1 medium onion, finely chopped (~1 cup chopped)
1/3 cup chopped fresh parsley
1 medium clove garlic, finely minced or pressed with a garlic press
3 tablespoons buttermilk (or milk)
2 teaspoons kosher salt (or to taste)
1/2 teaspoon ground black pepper

1. Wash the potatoes and trim off any bad spots.
2. Add the whole potatoes (skin on) to a large pot of salted water, and bring to a boil.
3. Simmer the potatoes until they are tender throughout; test by piercing with a fork or knife. This will likely take anywhere from 20 to 40 minutes, depending on the size of the potato; we check the potatoes about every five minutes once they've been cooking for 20 minutes. Remove any small potatoes that finish cooking before larger ones.
4. Drain the potatoes and let cool to a comfortable handling temperature (but do not refrigerate).
5. Cut the potatoes into bite-sized pieces and put into a bowl.
6. Mix the mayonnaise, onions, parsley, garlic, buttermilk, salt, and pepper in a separate bowl.
7. Add the mayonnaise mixture to the potatoes, and mix gently.
8. Refrigerate for at least a few hours to allow the flavors to meld; we serve it cold.

Notes:

Vary the amount of onion to suit your tastes; we prefer it very oniony, but if you want it milder, use less onion or use a sweet onion. If at all possible use fresh parsley, as dried parsley isn't nearly as flavorful.

We typically don't worry about the variety of potatoes we use, though in general waxier potatoes hold their shape better. Last night we used "Butter Golds" and they were very good.