Add mashed potatoes, egg, and a pinch of salt to a large mixing bowl.
Add 1/4 cup of flour to the bowl and gently stir to combine. The amount of flour you need will vary based on your mashed potato recipe – I find I usually need around 1 cup to get a gnocchi consistency I like. I recommend adding flour 1/4 cup at a time until the dough feels right. You can mix the first bit of flour in with a spoon or spatula, but after that it’s helpful to use your hands to finish mixing. When the dough is ready, it should be soft and light, but not sticky. Avoid overworking the dough – this can cause chewy, gummy gnocchi
Lightly flour a large cutting board and a sheet pan or large plate.
Use a knife to divide gnocchi dough into 4 or 5 sections. Place one section of dough on the cutting board and use your hands to gently roll it into a long rope, about 1/2″ thick. If the dough gets sticky as you roll it, dust it with some extra flour.
Use a knife to cut the rope of dough into 1/2″ pieces – these are your gnocchi! Transfer the cut gnocchi to your lightly floured sheet pan and repeat the rolling and cutting process with the remaining dough. If you’d like, you can roll each gnocco across a gnocchi board or the tines of a fork to form ridges (see recipe notes).
Bring a large pot of water to a boil and add a generous pinch or two of salt.
Carefully add gnocchi to boiling water give them a gentle stir. Cook for 2-3 minutes until gnocchi float to the top of the water. Drain and toss with your favorite sauce.