Spread the walnuts on a baking tray and roast for 7-8 minutes, until lightly browned. Allow to cool.

Meanwhile, put on a thick pair of gardening gloves (or washing up gloves), and pick the leaves from the nettles, discarding all the thick stalks. Wash the leaves thoroughly under running water.

Bring a large pan of salted water to the boil. Add the washed nettles and blanch for 20-30 seconds, until just wilted. Quickly remove the nettles from the water using a slotted spoon and plunge into a bowl of iced water. Once the nettles are cool, remove from the bowl and squeeze out as much water as you can (they will have lost their sting at this point so you can do this with your hands!).

Combine the roasted walnuts, nettles, pine nuts, garlic, basil, lemon juice and a good pinch of salt and black pepper in a food processor. Blend, adding the extra virgin olive oil in a slow drizzle through the hole in the top, until almost smooth (you want it to retain a little bit of texture). Taste and adjust the seasoning, if needed.

Spoon the pesto into an airtight jar and keep refrigerated for up to a week.