FOR THE GNOCCHI:
1 lb. russet potatoes (about 2), unpeeled
1 1⁄4 cup flour, plus more for dusting
3⁄4 tsp. kosher salt
1 tbsp. truffle oil
1 egg, beaten
FOR THE SAUCE:
2 tbsp. extra-virgin olive oil
10 oz. mushrooms, preferably chanterelles,
2 cups heavy cream
3⁄4 cup peas, fresh or frozen
2 tsp. finely chopped fresh thyme
Kosher salt and freshly ground black pepper,
1 tbsp. finely chopped chives
1. Make the gnocchi: Boil potatoes in a 4-qt. saucepan of salted water until tender, about 20 minutes. Drain the potatoes; let cool slightly and peel. Work potatoes through a food mill or a potato ricer onto a lightly floured surface. Sprinkle the flour and salt over the potatoes and mix together with your hands. Form a mound and create a well in the center; add truffle oil and egg. Gently knead dough until it just comes together, adding a little more flour if it begins to stick.
2. Lightly flour a parchment paper–lined baking sheet and set aside. Using a rolling pin, roll dough to a 1⁄2" thickness. Cut into 1⁄2"-wide strips. Roll each strip between your hands and the work surface to form ropes. Cut each rope into 1" segments. Working with one segment at a time, roll it down the back of a small fork so that the tines make ridges on the surface of the dough (see How to Roll Gnocchi). Transfer gnocchi to the prepared baking sheet; cover with a kitchen towel and refrigerate until ready to cook.
3. Make the sauce: Bring a 6-qt. pot of salted water to a boil. Heat oil in a 12" skillet over medium-high heat. Add mushrooms to skillet and cook, stirring occasionally, until light brown, about 5 minutes. Raise heat to high; add cream, peas, and thyme and cook, stirring occasionally, until cream reduces by half. Season mushroom sauce with salt and pepper and remove skillet from heat. Boil gnocchi in the salted water until they float, about 2 minutes. Using a slotted spoon, transfer gnocchi to mushroom sauce, add chives, and toss to combine.