1- Clean the spinach, removing any damaged leaves, wash several times in plenty of cold water, drain and cut into strips.
2- Peel the clove of garlic, wash and crush lightly. Wash the anchovies under running water to remove all the salt, then remove the heads and the backbone and cut the fillets into pieces.
3- Bring a saucepan of salted water to the boil and cook the pasta. In the meantime, put the oil in a pan and fry the garlic until just golden; add the pieces of anchovy and melt on a medium heat, stirring with a wooden spoon.
4- Add the strips of spinach, season with a pinch of salt and pepper and fry for 2-3 minutes, stirring all the time.
5- Drain the penne when they are “al dente”, pour them into the pan containing the strips of spinach, add a few spoons of the pasta cooking water, leave to absorb the flavours for a minute and serve hot.