To make the dressing, combine all the ingredients in a bowl and season well.
Bring a pan of salted water to the boil and fill a bowl with iced water. Cook the asparagus for 2 mins, then transfer to the iced water with a slotted spoon. Cook the beans for 4 mins and repeat, then do the same with the broccoli (cook for 2½ mins) and peas (cook for 1 min). Drain and pat dry with kitchen paper.
Tip into a bowl with the radishes, cabbage, spring onions and mint. Serve the dressing on the side.
