Gnocchi with watercress and hazelnut pesto

1. Preheat the oven to 200°C, gas mark 6. Prick the potatoes with a fork; put on the top shelf of the oven. Bake for 1 hour, until the flesh is soft to the point of a knife.

2. Meanwhile, make the pesto. Put the hazelnuts, garlic and a large pinch of salt in the small bowl of a food processor; whizz until roughly chopped. Add the watercress (reserve a little to garnish), lemon juice and oil and whizz again, until combined but still with a little texture. Scrape down the sides with a spatula. Cover and keep in the fridge for up to 3 days, stirring well before use.

3. Sift the flour into a mixing bowl with the salt. Once the potatoes are cooked, hold them with a tea towel and cut them in half, then scoop out all of the flesh with a spoon. Then, wearing protective gloves, use a potato ricer or fine grater to grate the flesh over the flour. Add the egg and bring everything together with a wooden spoon. As soon as the mixture begins to clump together, use clean hands to lightly knead it into a smooth dough. Don’t overwork the mixture.

4. Dust the work surface with a little more flour, then tip out the dough and pat into a 2-3cm thick square. Cut into 2cm-wide strips and roll these gently to smooth the edges and create long sausages. Cut into 1cm-long gnocchi, dusting with flour and rolling each over the tines of a fork while pressing with the pad of your thumb to create light indentations.

5. Bring a large pan of salted water to the boil; reduce to a gentle simmer. Add ½ the gnocchi. Stir once and wait for them to rise to the surface (this should happen within 1 minute). Cook for 15 seconds more, then remove to a plate with a slotted spoon. Repeat with the other ½. Gently toss the gnocchi with the pesto to coat, then season. Divide between plates and serve at once, garnished with the reserved watercress.