Direction

1. Preheat the oven to 375º. In a 9-inch square baking dish, brush the beets with olive oil and season with salt and pepper. Add 1/4 cup of water to the baking dish and cover tightly with foil. Bake the beets for about 1 hour, until tender. Uncover the dish and let the beets cool completely.
2. Peel the beets and cut them into 1-inch pieces. Transfer the beets to a food processor and puree.
3. In the bowl of a standing mixer fitted with the paddle, combine 1 1/2 cups of the beet puree (reserve any remaining puree for another use) with the ricotta, egg, nutmeg, the 3/4 cup of Parmigiano and 1 tablespoon of salt and mix at low speed until combined. Using a rubber spatula, scrape down the side of the bowl. Sprinkle on the 3 cups of flour and mix at low speed until the dough just comes together, about 1 minute.
4. Scrape the dough onto a lightly floured work surface and knead gently just until smooth but still slightly sticky. Cover the dough with plastic wrap and let stand at room temperature for 30 minutes.
5. Line a baking sheet with wax paper and generously dust with flour. Cut the gnocchi dough into 10 pieces and roll each piece into a 1/2-inch-thick rope. Cut the ropes into 1/2-inch pieces and transfer the gnocchi to the prepared baking sheet.
6. Lightly oil another baking sheet. In a large, deep skillet of simmering salted water, cook one-fourth of the gnocchi until they rise to the surface, then simmer for 1 minute longer, or until they are cooked through. Using a slotted spoon, transfer the gnocchi to the oiled baking sheet. Repeat with the remaining uncooked gnocchi.
7. In a very large skillet, toast the chopped walnuts over moderate heat, tossing, until golden and fragrant, 3 to 5 minutes. Transfer to a plate and let cool.
8. Add the butter to the skillet and cook until golden brown, 2 to 3 minutes. Add the sage leaves and cook for 20 seconds, then stir in the lemon juice. Add the gnocchi and cook for 1 minute, tossing gently. Season with salt and transfer the gnocchi to plates. Sprinkle the toasted walnuts on top and serve, passing grated Parmigiano-Reggiano at the table.