Preheat an oven to 375ºF. Prick the potatoes all over with a fork. Pour a small mound of kosher salt in the middle of a rimmed baking sheet, then nestle the potatoes on top of the salt. Bake the potatoes until tender (45 minutes – 1 hour). While the potatoes are still hot, carefully remove the skins. They should come off easily, but you can use a paring knife if there are any stubborn bits. Chop peeled potatoes (still warm) into large chunks, and press through a ricer on to a lightly floured work surface. Let cool for 3 to 4 minutes.

Bring a large pot of water to a boil, then add 2 big pinches of kosher salt. Form a well in the middle of the riced potatoes. Sprinkle 1/2 cup flour around the well, then crack and egg in the middle (see image). Using a fork, beat the egg in a circular motion, gradually pulling some flour and potato from the sides of the wells. Keep using the fork until the egg is incorporated, then knead the dough with your hands just until it comes together. If you are finding that the dough is too sticky, you can add flour (in small amounts) until the dough becomes smooth. Do not overwork the dough here. Pinch off a small bit off dough, and toss it into the boiling water to make sure it will hold its shape. If it doesn’t, knead in a bit more flour, and test again. Divide dough into 4 pieces, then roll each piece into a 1/2-inch thick rope. Cut each rope into 1/2-inch lengths. Transfer to a parchment-lined baking sheet, and set aside while you prepare the sauce.

Melt butter in a large skillet over medium heat. Cook until the butter turns a light brown color and smells nutty. Add the sage leaves, and let sizzle for 1 minute. Take the sauce off the heat. Drop the gnocchi in the boiling water, and stir. As soon as the gnocchi float to the surface, they are done (30 seconds to 1 minute). Return the brown butter sauce to medium-low heat. Using a slotted spoon, scoop the cooked gnocchi into the brown butter sauce, tossing to coat. Add a pinch of red pepper flakes (to taste) and 2 tablespoons of the gnocchi cooking water, tossing to combine. Remove from the heat and top with Parmesan cheese. For a nice presentation, you can shave the cheese with a vegetable peeler. To serve, spoon gnocchi into shallow bowls, and top with more Parmesan cheese to taste.