1tbspextra-virgin olive oilthe authors recommend using Odysea extra-virgin olive oil
For the miso butter
1tbspdark soy sauce
Bring a large saucepan of salted water to the boil. Tip in the potatoes and gently boil them for 15–20 minutes, until tender, then drain and allow to cool slightly
While the potatoes are boiling, make the herb vinegar. Whizz all the ingredients together in a food processor until finely chopped. (Or, very finely chop up the herbs and chilli and mix them in a bowl with the vinegar and oil.) Set aside.
Just before the potatoes are ready, make the miso butter. Place a large frying pan over a medium heat and add the miso, butter, pepper and soy sauce. Allow to melt, then whisk vigorously to combine. Once you have drained the potatoes, add them to the miso butter in the pan, smashing them down lightly with a spatula and cooking and turning them for a couple of minutes to coat.
Spoon the potatoes into a serving dish and drizzle with the herb vinegar to serve.