Cut the mushrooms into very small pieces and sauté them with olive oil over high heat.

When the mushrooms have released their water, add salt and tomato paste for 1 minute.

Let the mushrooms cool.

Cut the onion into very small pieces and sauté it with olive oil in a small saucepan over low heat for 10 minutes.

Add the grated garlic cloves for 1–2 minutes.

Let the onion mixture cool.

Pulse the seitan in a blender.

Mix everything with chopped parsley, Parmesan, beaten egg, breadcrumbs, salt and pepper.

Form the meatballs and chill them for at least 30 minutes.

Heat a generous drizzle of olive oil in a non-stick frying pan.

Before adding the meatballs, roll them again between your hands so they are firm.

Grill the meatballs on all sides.

Set aside any meatballs you will not eat immediately and, once cooled, freeze them in a freezer bag.

Take a sheet of baking paper, fold it in quarters and then accordion-fold it.

Place the end of the paper in the centre of the frying pan and cut off what extends beyond the pan.

Add the Arrabiata sauce and the paper lid.