Finely grated zest and juice of 1 lemon, plus more lemon juice for serving
2teaspoons minced fresh rosemary
1tsp fine sea salt, more pen
1tsp coarsely ground black pepper
Dash or two of hot sauce
⅓cup extra-virgin olive oil, more for drizzling
2tbsp mayonnaise, sour cream or crème fraîche
1tbsp Dijon or whole-grain mustard
½cup thinly sliced scallions (white and green parts)
¼cup chopped parsley
2tbsp chopped basil or dill
Cook the potatoes in a pot of well-salted water until they are very tender but not mushy, 15 to 22 minutes. Drain well.
In a large mixing bowl, whisk together lemon zest and juice, rosemary, salt, pepper and hot sauce. When the salt is dissolved, whisk in the olive oil, mayonnaise and mustard.
Add potatoes to the bowl and mix them very well, until well coated with dressing. Then use the spoon to mash about a quarter of them. You want 1-inch (or so) chunks of potatoes coated in some mashed potatoes. Add scallions and parsley and toss well. Taste and add more salt, lemon juice, hot sauce and olive oil, if needed. Scatter chopped basil or dill over dressed potatoes. Serve warm or at room temperature, but not cold.