Wash the potatoes and drain excess water in a colander. Cut the potatoes in half and set aside.

In a large pot, add cold water. Place the potatoes in the pot and add salt. Cover pot with a lid and bring up to the boil. Once the water has boiled, remove the lid and cook potatoes until soft, roughly 10 minutes.

To test if potatoes are cooked, use a pointed knife and poke a potato with the tip. If it goes in and slides out easily, the potatoes are ready. Turn off the heat and drain potatoes in a colander. Transfer to a large mixing bowl and set aside to let them cool down.

Meanwhile, finely slice the onion and cornichons and transfer to the same bowl.

Now add mayonnaise and a dollop of mustard (I used Thomy mustard). Stir together. Add white ground pepper and salt to taste and gently incorporate together.