Method

• 1

  Cut the potatoes into even-size pieces, then cook in lightly salted water, for 15 minutes until tender; drain very well.

• 2

  While the potatoes are cooking prepare the watercress pesto. Trim stalks from watercress, dry on kitchen paper, reserve a few sprigs for garnish. Then put the rest into a food processor with the garlic, salt and walnuts and pulse until finely chopped. Add the oil and cheeses and give a quick whizz until blended.

• 3

  Drain the potatoes very well then push through a potato ricer into a bowl, as the mash needs to be completely lump-free and have a dry texture. Add the flour and egg with seasoning and work with a fork to form a smooth, soft dough.

• 4

  With floured hands take a piece of the dough and roll it into a roll about 2cm in diameter, then place on a floured surface and cut into 2cm lengths. Gently press one side with a fork to make a ridged surface. Place the gnocchi on a floured tray until ready to cook.

• 5

  When all the dough has been shaped, bring a large pan of salted water to the boil. Gently add the gnocchi, and poach a few at a time for 2-3 minutes; as they rise to the surface remove with a slotted spoon and drain. Slide them into a hot serving dish.

• 6

  Add the prepared pesto and mix together, serve scattered with vegetarian Parmesan-style cheese and the reserved watercress leaves.