Bring a large pot of salted water to a boil, and add the peeled potatoes>
Cook until tender but still firm, about 15 minutes.
Drain, cool and mash with a fork or potato masher.
Combine 1 cup mashed potato, flour and egg in a large bowl. Knead until dough forms a ball. Shape small portions of the dough into long "snakes". On a floured surface, cut snakes into 4cm pieces.
To cook the gnocchi
Bring a large pot of lightly salted water to a boil. Drop in gnocchi and cook for 3 to 5 minutes or until gnocchi have risen to the top; scoop out with a slotted spoon and drain on paper towel.
In a large saucepan over a medium to low heat, gently melt the butter with the garlic and sage until the mixture turns golden brown in colour, and is nutty and fragrant.
Pat dry the cooked gnocchi and add to the pan. Toss for 30 seconds to 1 minute, or until the dumplings develop a golden crust.
Season to taste, then serve directly from the pan, topped with grated Parmesan.