Tip the flour onto a clean work surface and make a little well in the centre.
Place the butter in the well and work it into the flour with your fingertips. Sprinkle over the yeast and pour in the water, a little at a time, incorporating it as you go.
Finally, sprinkle over the salt and combine well. Knead the dough for 10 minutes, by which time it should be smooth, soft and elastic. Alternatively, you can make the dough using a stand mixer with a dough hook attachment on low speed.
Transfer the dough to a medium-sized bowl, cover with an upturned plate and set aside to rest in a warm draught-free place for 2 hours, or until doubled in size.
Place the dough on a lightly floured work surface and roll out to a 3-4 millimeter (1/4 inch) thick rectangle.
Using a fluted pastry cutter, cut out 8 centimeter x 10 centimeter (3 1/4 inch x 4 inch) rectangles. You can also cut triangles or diamonds if you like.
Heat 3-4 centimeters (1 1/4-1 1/2 inches) of oil in a heavy-based saucepan (or use a deep-fryer) to 190˚C (375˚F). Test the heat of the oil by dropping in some pastry scraps. If they sizzle straightaway, the oil is ready.
Carefully drop in 1-2 'gnocchi' (depending on the size of your pan). They will take 30-40 seconds to cook on each side and will puff up quite a bit. When one side is golden, flip over and cook the other side.
Drain on kitchen towel and eat warm or cool, served with slices of prosciutto or salame.
These are best eaten on the day they are made.