The dough in this recipe is that of gnocchi, the dish of the taverns, loved by children, tasty and simple, but above all very nutritious. It is from this last characteristic that the Roman saying ‘Thursday gnocchi, Friday fish, Saturday tripe’ originates: gnocchi, in fact, are energetic and tasty, perfect as a hearty meal before the day of fasting or abstention from meat, which according to Catholic tradition is Friday.
This poor recipe, which required only a few readily available ingredients (potatoes, flour, eggs and water), today has many versions, enriched with butter, spices, vegetables, depending on the season.
The potato roll proposed by Andrea can be filled as desired and follows all the necessary rules for preparing perfect gnocchi: small tricks that grandmothers have revealed over time to their children and grandchildren, handing down an extraordinary culinary tradition.

Wash the potatoes and cook them in salted water with their skins on. Once cooked, peel them while still hot (you can use a tea towel to avoid burning yourself) and mash them with a potato masher.
Let them cool slightly, knead them first with the eggs and salt, then with the flour, until the mixture becomes uniform.
Blanch the spinach in salted water for 10 seconds and pan-fry with a little oil and a crushed clove of garlic, stirring until dry; season with salt and pepper.
Prepare a pot at least 20-30 cm wide and 15 cm deep with salted water and bring to the boil.

Roll out the dough on a lightly floured cloth to a rectangle about one centimetre thick. Spread the spinach on top of the dough, roll it up starting from the long side and try to form a cylinder, helping yourself with the tea towel and tightening it as much as possible.

Roll up and tie the ends, plunge the resulting cylinder with the tea towel into the pot of gently boiling water and cook for 30 minutes.
In the meantime, gently melt two knobs of butter with the sage, a pinch of salt and pepper for flavour: remove from the heat before the butter starts to sizzle.
Drain the roll, let it rest for at least 10 minutes, remove it from the tea towel and cut it into slices.