In a large pot, cover yams with cold water. Bring to a boil and cook until tender, about 20 minutes.
Once yams are cooked and cooled, remove skins. Pass yams through a ricer. Make sure yams are cool enough to touch.
In a bowl, mix the riced yams with the rest of the ingredients (1/2 cup flour at a time) until well combined and a dough is formed, about 3 minutes. if dough is too sticky, add more flour.
Cut dough ball into 8 even pieces. On a floured surface, use your hands to roll one dough ball into a long cylinder/snake shape about 1/4 inch in diameter. Use a pastry scraper or knife to cut 1/2-inch pillows. Holding a fork at a 45-degree angle, roll the gnocchi pillows off the back of the fork to create the traditional gnocchi divots. Cover gnocchi with a dish towel while you finish making the rest.
Bring a large pot of salted water to a boil. Add gnocchi and cook until they float to the top. Cook for 1 minute longer, strain and serve plain or with desired sauce.