A bowl of homemade gnocchi, finished with a grating of Parmigiano-Reggiano, is a simple pleasure: few things compare to the light, pillowy texture of made-from-scratch gnocchi. You can vary the size and shape of the pasta, even use a mixture of different types of potatoes for a depth of flavor, but this essential, basic version is easy to execute and serve to guests.
Place the potatoes in a large stock pot, cover with cold water and, add 1 teaspoon salt. Bring the pot to a simmer, and cook until the potatoes are soft and yield easily when poked with a knife, about 45–55 minutes.In a small saucepan set over medium-low heat, melt the butter and rosemary. Remove from the heat and let the rosemary steep while the potatoes cook.Remove the potatoes from the water, let cool slightly, and peel while still warm. Using a food mill fitted with the plate with the smallest holes, mill the potatoes into a large mixing bowl. Season the potatoes with 1 teaspoon of salt.Discard the rosemary from the melted butter. Add the cream, eggs, egg yolks, melted butter, and a few swipes of fresh nutmeg to the potato mixture. Stir to combine.
Mound the flour on a clean work surface. Create a well in the center of the flour, and pour the potato mixture into the well. Using a bench scraper, gradually cut the flour into the potato mixture, until all of the potato has been incorporated, and the dough is loose and shaggy. Bring the loose dough together with the bench scraper. Turn the dough a few times using the bench scraper, to incorporate some of the excess flour that remains. Before you add all of the flour, test the gnocchi by rolling and poaching a few. Test the dough additionally by poking it with your finger. If your finger is easily removed and the dough isn't sticking to it, then it's ready to roll and shape. Roll the dough into long, thin ropes, and cut into half-inch pieces. Gently roll the pieces over the tines of a fork with your fingers, to achieve the traditional shape of the pasta. Use a generous dusting of flour to help hold the shape of the pasta. Repeat with the remaining dough. The gnocchi can be stored in the refrigerator (on a rimmed baking sheet, generously dusted with flour) for up to 24 hours.
Once the dough has been tested and rolled, bring a pot of heavily salted water to a rolling boil. Drop the gnocchi in the water and poach for a few minutes, until they start to float. Remove with a slotted spoon.
To serve the gnocchi, melt a few additional tablespoons of butter in a medium sauté pan. Add the poached gnocchi and toss to coat. Add a few splashes of the salted pasta water to the pan, and taste for salt. Divide into shallow bowls and garnish with a generous grating of cheese. Serve immediately. Fontina Sauce (optional, not in video):In a medium, heavy-bottomed saucepan, warm 2 cups heavy cream over medium-low heat. Add cream to a blender, and turn on low. Add 1½ cups grated Fontina and continue to blend until a smooth sauce is formed. Thin with ½ cup vegetable stock, as necessary. Season with salt and freshly grated nutmeg to taste.