Steps
- Simmer 1kg of waxy potatoes in water for 25-30 minutes, until fork-tender. Drain, cool slightly, peel, and slice ⅛in / 3mm thick.
- Melt 2 tablespoons of unsalted butter in a skillet over medium heat. Cook 1 finely diced yellow onion for 3-4 minutes, until translucent.
- Add 80ml of white wine vinegar, 200ml of vegetable broth, and 1 teaspoon of salt. Bring to a boil, then simmer for 2 minutes.
- Pour over the potatoes and gently stir in 2¼ teaspoons of tarragon mustard, followed by 80ml of sunflower oil. Cover and rest for 30 minutes; stir and garnish with chopped parsley.