For the pickled onions, mix the vinegar and sugar with a pinch of salt until the sugar dissolves. Add the onion, cover and leave to pickle. To make the chipotle ‘mayo’, put all of the ingredients into a small blender (or use a stick blender) with a pinch of sugar and whizz until very smooth. Add 2 tbsp olive oil, whizz again until it looks like mayonnaise. Season, tip into a bowl, cover, and chill.