Combine the flours and salt in the bowl of a stand mixer with the egg and mix, slowly drizzling in the water until a rough dough forms. Continue to work the dough until it comes together, about 5-10 minutes on the lowest speed setting.
When the dough cleans the sides of the bowl and comes together in a solid mass, remove it from the mixer and allow to rest, wrapped in plastic for 30 minutes.
Alternately, pile the flour and salt into a mound on a cutting board and make a well in the center, then add the eggs and mix together with a fork, gradually adding the water as needed and working the mixture with your hands.