It is adapted from celebrated Seattle chef, Ethan Stowell.
1 cup extra-virgin olive oil
Champagne vinegar
Kosher salt and freshly ground black pepper
2 celery hearts, thinly sliced (about 4 cups)
2 bunches radishes, thinly sliced
8 small scallions, white and light green parts only, thinly sliced (1 cup)
Bring a large pot of salted water to a boil. Add the potatoes and cook until tender, about 20 minutes. Drain and let cool. Slice the potatoes 1/2 inch thick.
Meanwhile whisk the olive oil with the vinegar and season with salt and pepper. Gently fold in the potatoes and celery.
Let stand at room temperature until cool, about 30 minutes. Just before serving, fold in the radishes and scallions and season with salt and pepper.
Make Ahead: Bring to room temperature before adding the radishes and scallions.