If ay of your potatoes are larger than the others, cut them in half so that all of the potato pieces are approximately the same size.
Boil the potatoes in a large pan of water for around 15 minutes, or until soft. Add the asparagus for the last 4 minutes or so of cooking. When both vegetables are tender (the asparagus should still have a slight crunch), drain, and set aside to cool completely.
To make the mint and pistachio pesto, add the garlic, mint, parsley and pistachios to a mini food processor, along with a good pinch of salt and pepper. Blitz to form a coarse paste. If using, add the Greek yogurt, and blitz again to combine.
When the potatoes have cooled completely, add them to a large bowl, along with the pistachio pesto, sweetcorn, cherry tomatoes, and some more whole pistachios. Mix well to combine, and serve slightly chilled.