2 pounds small red, white, and purple potatoes, scrubbed and sliced into ¼-inch thick rounds
1 tablespoon sea salt
¼ cup olive oil
⅓ cup fresh dill, finely chopped, plus about 2 tablespoons more for garnish
⅓ cup finely chopped green onions, plus about 2 tablespoons for garnish
2 tablespoons fresh lemon juice
2 teaspoons Dijon mustard
2 cloves garlic, finely chopped
Freshly ground black pepper, to taste
3 stalks celery, chopped
Place potatoes in a large saucepan and cover with water. Add salt and bring to a boil. Once boiling, reduce heat to medium-low and cook until potatoes are easily pierced by a fork, about 5 to 6 minutes.
Reserve ¼ cup cooking water, then drain. Transfer the potatoes to a large mixing bowl.
In a small bowl, combine the olive oil, ⅓ cup dill, ⅓ cup green onions, lemon juice, Dijon mustard, garlic, freshly ground black pepper, and reserved cooking water. Whisk until well blended.
Pour the olive oil mixture over the potatoes and gently mix to combine. Let the potatoes sit for ten minutes, gently tossing every few minutes.
Add the celery to the bowl, along with the rest of the dill and green onions. Toss again. Season to taste with salt and pepper.
Serve immediately, or cover and refrigerate until you’re ready to serve.