In a large pot, boil the potato in water until tender; then grate.
Mix flour, potato, and salt together thoroughly.
Make a well and drop in the egg, then beat with a wooden spoon.
Add as much cold water as needed to hold the dough together (about 1/8 of a cup).
Mix vigorously until the dough starts to blister and come away from the sides of the bowl.
Let rest for at least 45 minutes, then turn out on a wet cutting board and using a knife to cut off pieces about 1/2-inch long and approximately the width of a pencil.
Drop the pieces into a large pot of boiling water (the same pot you used to boil the potato).
A few seconds after they float to the surface remove them with a slotted spoon and let them drain.
Make roux by heating butter in a saucepan and stirring in the flour, pepper, nutmeg and parsley; continue stirring constantly for 3-5 minutes then dilute with stock, blending thoroughly to be sure that there are no lumps.
Add salt, sugar, and brandy or extract and bring to a boil.
Add the asparagus and simmer, uncovered, just until the asparagus is tender (5-10 minutes).
Mix in cream.
Taste for seasonings and simmer for 5 more minutes.