Cook the potatoes and eggs together. Place the potatoes in a large pot and cover them with cold, salted water by about 3cm. Gently lower the eggs into the same pot. Bring to a steady, rolling boil over high heat. Once boiling, reduce to a simmer and cook for 10 minutes. The water will smell faintly earthy and clean. After 10 minutes, remove the eggs with a slotted spoon and plunge them into a bowl of ice water. Continue cooking the potatoes for another 8-10 minutes, until a knife slides into the thickest part with just a little resistance. The skin will look slightly crackled, and the aroma will be warm and starchy.

Prepare the dressing. While the potatoes cook, make the creamy base. In a small jar or a bowl, combine the mayonnaise, yogurt or soured cream, wholegrain mustard, and white wine vinegar. Add the sugar if using, plus a generous pinch of salt and a few grinds of black pepper. Screw the lid on the jar and shake vigorously, or whisk in the bowl until the dressing is completely smooth, pale, and glossy. The smell will be tangy and rich, promising a lovely balance.

Drain and steam the potatoes. Drain the potatoes in a colander and let them sit for 2-3 minutes. They should be steaming gently. This step is key; the residual heat helps the potatoes absorb the dressing. The steam will smell clean and pure, a sign they are perfectly cooked.

Combine the warm potatoes with the dressing. Tip the hot, steaming potatoes into a large salad bowl. Pour over about two-thirds of the dressing and fold gently with a large spoon, being careful not to break the potatoes. You want each piece to be lightly coated. The warm potatoes will drink in the dressing, creating a wonderfully creamy interior. Let this mixture cool completely at room temperature for about 20 minutes. The colour will deepen to a pale, buttery yellow.

Prepare the additions. While the potatoes cool, peel the hard-boiled eggs and chop them into a small dice. Finely dice the red onion and celery. Pick the parsley leaves from their stems and chop them finely, then snip the chives. The vibrant green of the herbs and the sharp, fresh scent of the onion and celery will fill the kitchen.

Finish the salad. Once the potatoes are at room temperature, add the chopped eggs, red onion, and celery to the bowl. Pour over the remaining dressing. Gently fold everything together until it’s all well combined. The mixture should look creamy and inviting, with specks of green and pale yellow throughout. Taste and adjust the seasoning, adding more salt, pepper, or a splash of vinegar if needed. My husband, who's usually picky, asked for seconds!

Rest and serve. For the best flavour, cover the bowl and place it in the fridge for at least 1 hour, or overnight. This resting time is crucial; it allows the flavours to meld and deepen. Just before serving, sprinkle the snipped chives and chopped parsley over the top for a fresh, vibrant finish. The final texture should be creamy, with tender potatoes that are full of flavour.