Bring a pan with water to the boil, add the nettles and leave it to boil for 4-5 minutes.
Drain the liquid, add the nettles to a collander, and use a wooden spoon to press down well to drain as much liquid as you can.
Transfer the nettles to a chopping board and chop them roughly.
In a pan set over a medium heat, add the butter and oil, and allow the butter to melt.
Peel and chop the onion, and add it to the pan.
Season with half a teaspoon of salt, then leave the onion to fry until golden.
Add the chopped wild garlic and peeled and chopped potato.
Pour over the stock, place a lid on the pot, and leave it to cook until the potatoes are cooked through.
Add a few tablespoons of the hot liquid to the bowl of cream, so that the cream can be the same temperature as the soup.
Remove the pan from the heat, and add the tempered cream.
Season well with salt and pepper.
Use a hand blender to blitz it until smooth.
Serve hot!