Sicilian Bean and Potato Salad

I've made this potato salad for years. It's always popular with our friends and family. It's quick and easy to prepare. I've made it for so long now, it just wouldn't seem like summer without it. Since we were lucky enough to have a one of those unseasonably warm spring days a couple weeks ago I thought I'd make it for a friend of ours who was visiting from out of town.

1 pound of new potatoes, unpeeled.
1 pound of fresh green beans, steamed and cut into 1-inch lengths
1 cup of cooked cannellini beans
1 small red onion, finely chopped
1/2 cup black olives, pitted and sliced. (I always used small nicoise.)
1-2 tablespoons capers
Classic Vinaigrette (see below)
2 tablespoons freshly chopped Italian parsley
salt and pepper to taste

Vinaigrette
1-2 teaspoons of fine or grainy mustard
2 tablespoons of fresh lemon juice, or 2 tablespoons wine, balsamic, or cider vinegar
6 tablespoons olive oil
crushed garlic to taste
sea salt and black pepper to taste

In a medium saucepan, cook the potatoes in salted boiling water until they are tender. Allow them to cool slightly and cut them in half.

Mix the potatoes, beans, onion, black olives, and capers in a large bowl.

Pour sufficient vinaigrette over the salad to moisten it and toss well. Sprinkle with parsley and grated parmesan cheese and serve