1 onion, diced
1 rib celery, diced
1 carrot, peeled and diced
1 bay leaf
1/2 teaspoon whole black peppercorns
1 pound fingerling potatoes, scrubbed
1/2 cup olive oil
4 tablespoons red wine vinegar
1 can good-quality tuna in olive oil
2 tablespoons chopped capers
1/2 red onion, thinly sliced
1/2 cup picholine or other green olives, roughly chopped
1/4 cup chopped parsley
Small handful mizuna or arugula