Meanwhile, heat 1tbsp of the olive oil in a frying pan, add the onion and fry on a medium heat for 5 minutes or until coloured slightly and softened. Remove from the heat and tip into a large bowl, then add the cooked potatoe
Whisk 2 tablespoons of olive oil together with the vinegar, mustard and honey, then season. Pour it over the onions and potatoes and stir together.