Step 1

Make the basil pesto In a large pot of boiling water, blanch the basil until bright green, about 30 seconds. Immediately shock in a bowl of ice water. In the same pot, blanch the baby spinach until soft, about 2 minutes. Shock in the same ice water. Wring out the basil and spinach to release excess water and place in a blender.

Step 2

In a small pot, warm the cream and butter until the butter melts.

Step 3

In the blender, blend the basil and spinach until roughly chopped. With the machine running, slowly stream in the warm cream mixture. Add the Parmigiano-Reggiano and blend until a coarse paste forms. Season the pesto with salt and pepper.

Step 4

Make the gnocchi In a large pot of water, boil the potatoes until tender, about 30 minutes. Drain the potatoes.

Step 5

Line a large rimmed baking sheet with parchment paper. As soon as the potatoes are cool enough to handle, scoop their flesh into a ricer or tamis and rice the potatoes onto the parchment paper in a shallow layer. Let cool completely.

Step 6

Measure out 4 lightly packed cups of the riced potatoes and gently mix in the egg. (Extra riced potatoes can be used for more batches.)

Step 7

Add the flour in three batches, gently mixing until incorporated. Knead lightly to form the dough. Avoid overworking it, as that will create a heavy and dense gnocchi.

Step 8

Line a baking sheet with parchment paper. Divide the dough into quarters. Working with one piece at a time, gently roll the dough into a long rope about 1/2-inch wide. Using a sharp knife, cut the rope into 1/2-inch pieces. Roll each piece against the tines of a fork to make light ridges. Transfer the formed gnocchi to the lined baking sheet. Repeat with the remaining dough.

Step 9

In a large pot of boiling salted water, boil half of the gnocchi over high heat until they rise to the surface. Using a wire skimmer, transfer the gnocchi to a large bowl and toss with some of the pesto. Repeat with the remaining gnocchi and more pesto, season with salt and pepper and serve.