Add potato mixture to flour and 1 cup of reserved cooking water. (eatpicks.com)
Stir in noodles, adding 1/2 cup reserved cooking water. (vegetariantimes.com)
Add the noodles into the sauce, simmering until noodles have finished cooking, about 3 additional minutes (add reserved cooking water if sauce becomes overly dry and thick). (thespiffycookie.com)