Clean the artichokes in water with a dash of lemon juice, then trim and boil the hearts in a pan with salted water over a low heat for about 25 minutes.
Sauté the onion in a fairy deep frying pan with extra-virgin olive oil until it turns golden brown. Wash and cut the spinach into pieces and strain the artichoke hearts. Add to the onion, mix together and add salt and pepper.
To make the Béchamel sauce, warm the flour and walnut drink in another frying pan with extra-virgin olive oil, stirring all the while. Add a pinch of nutmeg and salt for some extra flavour.
Boil the penne following the instructions on the packet.
Mix the pasta with the onion, spinach and artichokes, then pour on the Béchamel sauce and stir well. Sprinkle a layer of Parmesan cheese on top and bake in the oven au gratin for 10 minutes.