Preheat oven to 350F (175C).
With a fork, puncture potatoes in several places.
Bake 1 hour or until tender.
Remove insides of baked potatoes; discard skins.
Mash hot potatoes through a ricer or food mill into a large bowl; let cool slightly.
Add egg yolk, 1 tablespoon salt and 2 cups flour; mix well.
Put potato mixture on a working surface or wooden board and knead into a ball.
Mixture should be soft and pliable and slightly sticky.
If it is too sticky, add more flour.
Lightly flour working surface and your hands.
Break dough into pieces the size of large eggs.
Shape pieces into rolls about the thickness of your thumb.
Cut rolls into 1-inch pieces.
Hold a fork with its tines resting on a work surface at a 45° angle and the inside curve toward you.
Take a dumpling roll and press it with your index finger against the outside curve of the fork at the tip end.
Quickly slide dumpling up and along the length of the tines, pressing with index finger.
Remove finger and let dumpling fall back onto work surface.
Grooves made by fork and finger indentation will absorb any sauce served with dumplings.
Repeat with remaining dumpling rolls.
Arrange dumplings on a floured tray or large plate.
Fill a large saucepan two-thirds full with salted water.
Bring water to a boil.
Add oil and dumplings.
When dumplings come to surface of water, cook 10 to 12 seconds.
If dumplings remain in water any longer they will absorb water and become too soft.
Remove dumplings with a slotted spoon or strainer, draining against side of saucepan.
Place in a warm dish.