Combine spinach and water in a saucepan. Cover and cook till spinach is very tender. Cool slightly.
Place spinach and liquid in a blender along with the egg and salt. Blend till smooth. Transfer to a bowl. Add enough flour to make a stiff dough.
Turn dough out onto a lightly floured surface. Knead for 1 minute. Roll out very thinly on a floured surface. Cover and rest for 20 minutes. Roll dough up loosely. Cut into 5cm wide lengths. Unroll. Cut into desired lengths. Spread out on a rack to dry for 2 hours.
Cook as for any fresh pasta in plenty of rapidly boiling salted water. Drain in a colander and use as desired.
Fresh pasta needs only a few minutes in boiling water and it's done. It is finished cooking when the pasta rises to the surface.