Image credit to: Boston Organics
Boil the potato in salted water and while it's still warm, carefully peel the skin. Using a fork, mash the potato in a bowl. Do not over mash but make sure there are no lumps.
Using a blender or food processor, grind arugula with egg yolk. Pour the mixture over the potato and roughly mix. Add a pinch of salt and shake some flour on top. Using a spatula, start working the dough. Keep adding flour as you go until the dough is moist but not sticky.
Roll the dough into a log and using a knife, cut into several pieces (approximately 5 or 6).
Work with one piece at a time. Dust some flour on it and roll it out to a much thinner log this time. Cut the thinner log into multiple pieces using a knife, each around 3/4 inches. Now using a fork or a gnocchi board, shape each piece. Place one piece at a time and press it with your finger lightly so it forms the ridges. Then, roll it to form a curl. (See the instructional video.) Set it aside and move on to the next piece.
Once you are done creating the gnocchi, bring a large pot of water to boil. When it does, get a separate pan ready by melting 1-tablespoon butter at medium heat. This will be used fry the gnocchi after boiling.
Boil the gnocchi (in batches, if your pot isn't large enough). It will take about 3 to 4 minutes for the pasta to become fluffy and float on top. Once your batch of gnocchi is done boiling, drain and drop it into the buttered pan, sautéing it for just a couple of minutes.
While the gnocchi sautés, heat another pan to medium-high, then add 3 tablespoons of butter. Once the butter is melted, stir in the lemon zest and chili flakes, if desired. In couple of minutes, the butter will turn brown in color. (Keep an eye as it can turn from brown to black quickly.) Finally, drop the sautéed gnocchi into the pan with brown butter and mix until the gnocchi is coated in sauce.
Serve by drizzling on some fresh lemon juice, a few shaves of parmesan cheese. Serves 2-4.