@a7 heres the gnocchi recipe i use and vriska really likes:
1 big potato
1 egg
1 cup of flour
per portion
peel and cook the potatoes, mash them (ideally with a proper potato masher, not just a fork)
mix in the potatoes with the eggs
add the flour
knead like any other dough

i'll have to do some testing, ideally italian pasta should have 50% hydration
potatoes are around 75-80% water
eggs are effectively 100%
so lets say you have 400g of potatoes and 150g eggs, the water content would be
400g * 75% + 150g = 450g
so the flour amount would be 900g
but i need to test
the thing with gnocchi is you can really play around with proportions depending on what you like, less or more eggs, less or more flour
you can even make gnocchi by just mixing mashed potato with eggs and rolling on flour, this won't be much of a dough but if you're a huge potato lover, might be the gnocchi for you