Pesto is, of course, available to buy everywhere, but it's also incredibly easy - and fun - to make at home.
30g pine nuts, toasted lightly in a dry pan for a few minutes
30g freshly grated Parmesan
1 clove garlic
Small squeeze of lemon juice
50-75ml olive oil
1. Cook the spaghetti according to packet instructions.
2. Put the watercress, Parmesan and pine nuts in a food processor and pulse them so that they are blended but still have some texture.
3. Add the oil, until you reach a consistency you\'re happy with. Stir in the Parmesan cheese and a squeeze of lemon juice.
4. Stir the pesto through the spaghetti and serve.