- 1
Place the unpeeled potatoes in a large pot, cover with cold water, add a pinch of salt, and simmer gently until a knife slides through the centers, about 35–45 minutes.
- 2
Drain the potatoes, let them steam-dry for 3 minutes, peel while warm, then pass them through a potato ricer onto a clean work surface.
- 3
Spread the riced potato into a thin layer and let it cool until warm, not hot, so the egg will not scramble.
- 4
Sprinkle the potato with salt, drizzle over the beaten egg, then scatter most of the flour over the top.
- 5
Fold and press the mixture together with a bench scraper or light hands, adding only enough remaining flour to form a soft dough; do not knead hard.
- 6
Divide the dough into 4 pieces, roll each piece into a rope about 2 cm / ¾ in thick, then cut into 2.5 cm / 1 in pillows.
- 7
Roll each pillow over a gnocchi board or fork to make ridges, then place on a floured tray in a single layer.
- 8
Make the pesto by blending basil, 30 g / 1 oz pine nuts, Parmesan, Pecorino, garlic, lemon zest, and olive oil until glossy but still fresh and green.
- 9
Toast the remaining 20 g / 0.7 oz pine nuts in a dry pan over medium-low heat until golden and fragrant, then set aside.
- 10
Boil a large pot of salted water, cook the gnocchi in batches, and lift them out with a slotted spoon 20–30 seconds after they float.
- 11
Loosen the pesto in a wide bowl with a splash of hot cooking water, add the gnocchi, and toss gently off the heat until coated.
- 12
Plate immediately with toasted pine nuts, extra Parmesan, basil leaves, and a thin drizzle of olive oil.