Cook the Sweet Potatoes:Oven Method: Preheat your oven to 400°F (200°C). Pierce the sweet potatoes with a fork and place them on a baking sheet. Bake for 45-60 minutes or until tender.Microwave Method: Pierce the sweet potatoes with a fork. Microwave them on high for 7-10 minutes until tender, and you can pierce them with a fork. Once cooked, let the sweet potatoes cool a bit, then peel and mash them and let them cool for a few minutes until you can handle them.
Make the Gnocchi Dough (note 1): In a large bowl or on your work surface, combine the mashed sweet potatoes, flour, and salt. Knead the mixture gently until it forms a smooth dough. If the dough is too sticky, add a bit more flour. You don't want to over-knead the dough, or the gnocchi will become too tough.
Shape the Gnocchi: Sprinkle a clean surface with flour. Take a small portion of the dough and roll it into a long rope about 1/2 inch in diameter. Cut the rope into 1-inch pieces to form the gnocchi. Coat the gnocchi with more flour to prevent them from sticking to one another.
Optional: Use a fork or a gnocchi board to create ridges on each gnocchi piece. Prepare the sauce: In a large skillet, heat the olive oil or butter over medium heat. If using butter, let it melt completely. Add the minced garlic and sage leaves to the skillet. Sauté for about 2-3 minutes or until the garlic is fragrant and the sage leaves are slightly crispy.
Cook the gnocchi: Bring a large pot of salted water to a boil. Cook the gnocchi in batches, they are done when they float to the top, about 2-3 minutes. Remove gently with a slotted spoon.
Mix: Add the gnocchi to the skillet with the garlic and sage. Toss gently to coat the gnocchi with the sauce. Sprinkle the grated Parmesan over the gnocchi and stir to combine. The heat from the gnocchi and sauce will help melt the cheese, creating a creamy texture.
Serve Immediately: Serve the gnocchi hot, garnished with additional Parmesan, black pepper, and sage leaves.