Potato Salad with Rocket, Shallots and an Anchovy Cream Dressing

During my childhood the idea of a potato salad used to make my heart sink. Now it makes it leap. The first potato salads I had were at school: small white cubes of wet potato coated in sour-tasting salad cream. It was not until years later that I realized a good potato salad can be an infinitely variable gastronomic thrill. Here is an example that is also practical and portable for taking on picnics.