Sift the flour in a big table, make a whole in the middle and pour the eggs, water and salt.
Mix with a fork starting in the center.
Mix with your hands until you form a ball. knead it by pushing down and away from you and turning it repeatedly until the dough feels smooth and satiny, 7 to 10 minutes. Let rest for at least 30 mins.
Roll the dough on a pasta machine until number one.
Scoop the celeriac puree on the rolled pasta leaving at least one inch of space in between each scoop. Place the egg yolk in the center of the puree.
Make an egg wash and brush around the the puree, this will help seal the ravioli. Laid another sheet of pasta on top.
Press with your fingers around the filling.
Cut with a ring cutter.
Store on the refrigerator, use semolina flour to keep from sticking together. When you are ready to serve it boil for 2 mins or until the ravioli floats to the top.
I served it with panchetta, roasted matsutake mushrooms and parmesan cheese.