Step 1

Boil the potatoes in a big pot of salted water until they're fork-tender. Drain, and shock in an ice bath if you want a potato salad that will maintain its shape. (If a few squished potatoes are okay with you, this step is not necessary.) While the potatoes cook, soak the red onion in a bit of water to soften its bite.

Step 2

Place drained potatoes in a large bowl, and sprinkle vinegar on them.

Step 3

Mix olive oil, mayonnaise, and mustard together to make your dressing, and set aside.

Step 4

To the large bowl, add the drained red onion, cornichon, hard-boiled egg, and herbs. Add the dressing -- starting with half, as you may not use it all -- and toss to coat. (You'll want enough dressing to slickly coat each potato, but you don't want a pool at the bottom of the bowl. If for some reason you find you need more dressing, add an extra splash of olive oil and a dollop of mayo to taste.) Add salt, and/or more vinegar to taste.

Step 5

When it's where you want it seasoning-wise, fold in the sliced radishes. Garnish with chives and/or chive blossoms if you like, and serve. It's even better after it's been in the fridge for a day.