Warm potato salad with pickled red onion

I’ve always thought of what are now fashionably called ‘crushed’ potatoes as ‘Irish’ potatoes. In French haute cuisine, you only get pommes mousseline (very creamy mash), whole or neatly shaped potatoes. But many spuds refuse to conform, falling apart before they are quite cooked. My favourite variety of potatoes for this dish is Désirée, which are quite well behaved and need a little