About 600g plain flour
1 tsp salt
1/2 tsp garlic powder
2 sage leaves
1/2 tsp smoked paprika
1 egg, beaten
Roast the sweet potatoes in their skins (pricking them all over first) at 200c for around 50 mins. When cool enough to handle peel them and mash or puree the flesh. You should end up with around 750g mashed sweet potato. Season with the salt, garlic powder and paprika and stir in the finely chopped sage leaves.
Stir in the beaten egg. Then add around 250g of the flour, beating it into the potato until combined. Gradually add more of the flour, until you have a smooth dough that isn't too sticky. Flour the work surface. You should be able to roll it into a sausage shape without it sticking to your hands too much.
Roll pieces of the dough into sausage shapes, around 2cm diameter. Then cut the sausages into diamonds or squares. Press each one with a fork to make indentations.
Bring a large saucepan of salted water to the boil. When boiling quite fiercely, drop the gnocchi in (in batches if you have too many) and cook them until they float to the surface. This will take around 3 minutes. Fish them out with a slotted spoon.
Serve with a garlicky tomato sauce, or sage butter, and some grated cheese and freshly ground black pepper.