Preheat oven to 210C and bake potatoes, skin on for about 45 minutes to 1 hour until cooked. Pierce with a small knife to test for doneness - it should pierce the potato easily. Alternatively, you can put the potatoes, skin on in a large pot of water and bring to the boil. Cook until just tender – avoid testing too often as puncturing them makes them waterlogged.
When they are done, drain and mash (or run through a potato ricer) while still hot. If you are using a ricer, you don’t even have to remove the skins.
Weigh out flour into a small bowl.
Add two thirds of the flour to the potatoes and knead just until it forms a smooth mixture – do not overwork the dough. Some potatoes absorb less flour than others, so it’s best not to add all the flour until you know exactly how much they will take. Stop adding flour when the dough starts to come together into one solid mass, and the mixture has become soft and smooth, but is still slightly sticky. If you need to, add a bit more flour - but use a gentle touch.
Dust the work surface lightly with flour. Break off a portion of dough and roll into a long thin sausage shape about 2.5cm thick. Repeat with the rest of the dough. Slice the rolls into 2cm lengths.
Holding a fork in one hand (or a gnocchi board if you have one) press each cushion of dough into the fork to make ridge on one side and a finger indent in the other. When gnocchi are shaped in this manner, the middle section is thinner and more tender in cooking, while the ridges become grooves for the sauce to cling to.
To cook the gnocchi, bring a big pot of water to the boil, and salt it. When boiling, drop in your first batch of 2-3 dozen gnocchi - 10 seconds after they have floated to the surface, drain them and taste. If they are too floury, add 2-3 seconds to the cooking time and if they are too sloppy/disintegrated/almost dissolved, subtract 2-3 seconds from the cooking time. Use that as a guide for the coming batches.
Remove gnocchi from boiling water with a slotted spoon and place straight into the sauce you are going to serve with.