Gnocchi with Arugula and Pecorino

Rinse the potatoes and cook for 25 minutes in boiling salted water. Remove, let dry, peel, and pass through a potato ricer. Cool slightly and mix with the flour, egg yolk, salt, and 1 pinch of nutmeg.

Rinse the arugula and trim off the thick stems. Dry thoroughly and finely chop half, then knead into the potato mixture.

Roll the dough into finger-thick rolls, cut into pieces, and indent with the tines of a fork. Rest on a cutting board for 15 minutes. Add the gnocchi to a pot with boiling salted water, then simmer for 5 minutes. The gnocchi are done when they rise to the surface. Remove and drain well.

Heat the butter, add the gnocchi, and toss until coated thoroughly.