- Preheat oven to 375˚F. Line a small baking dish with parchment paper. Prick yams a few times with a fork. Set in the baking dish and bake 60 to 70 minutes, or until very tender.
- Cool yams 15 minutes; until safe enough to handle, but still warm. Cut yams lengthwise in half and with a small spoon scoop out as much of the flesh as you can into a bowl. Discard the yam skins.
- Push yams through a food mill; thoroughly mash in the bowl by hand with a potato masher; or place in the bowl of your stand mixer and mash with paddle attachment until very smooth. Mix in the egg, 1/2 tsp. salt and nutmeg. Now mix in 1 1/3 cups of the flour until well combined.
- Lightly flour a work surface and transfer the dough on to it. Knead the dough, incorporating 1/2 to 2/3 cup more of the flour, as needed, into a pliable ball that is still slightly damp to the touch, but does not stick to your fingers.
- Divide dough into 3 equal pieces. Roll each piece into a 10” long log. Cut each log, widthwise, into 12 equal pieces. Flour your finger and make a deep dimple into each piece of dough.
- If desired, give gnocchi its traditional ridged look by rolling the non-dimpled side of each gnocchi over the tines of a floured fork, back of grater or with a gnocchi board. Set prepared gnocchi, not touching, on a parchment paper-lined baking sheet.
- Bring a large pot of lightly salted water to a boil. While that occurs, set a very large skillet over medium heat. When the skillet is hot, add the butter and oil. When butter has completely melted, add sage and cook until it becomes very fragrant and slightly crisp on the outer edges. Mix in garlic and blanched kale cook 1 minute more. Pour in chicken stock, and then turn heat off under the pan.
- When boiling, add half the gnocchi to the water and cook until they float to the surface, about 2 minutes. Scoop out the gnocchi with a slotted spoon and set in the skillet. Cook the remaining gnocchi and set them in the skillet too.
- Turn the heat under the skillet back to medium. Cook gnocchi in the sage/kale mixture 2 to 3 minutes, or until everything is hot. Sprinkle in salt, pepper and Parmesan cheese, to taste. Divide gnocchi among bowls and serve with additional Parmesan cheese for sprinkling on at the table.
Recipe options: The yams, after being pricked with a fork and set on a plate, could also be cooked in the microwave until tender. Do that in 2 minutes spurts. The total cooking time will be about 10 to 12 minute. Instead of kale, used chopped and blanched leaves of chard in this recipe.
To blanch kale, cook in boiling water 3 minutes. Drain kale well, cool in ice-cold water, and then drain well again, squeezing out as much water you can.