Mix spinach with egg yolks, salt, and pepper.
Add flour and mix until blended.
On a lightly floured surface, roll out dough 1/16 inch thick.
Cut into 4-inch squares.
Add squares one at a time to boiling salted water and cook about 2 minutes, or until tender.
Remove with a slotted spoon; cool separately.
Heat butter in a skillet.
Add onion, mushrooms, truffle, and chicken; cook about 10 minutes, stirring occasionally.
Gradually add milk, stirring constantly.
Mix in sherry and cheese.
Set aside Spoon filling along center of each pasta square and roll to form a tube.
Arrange rolls in a shallow baking pan and pour Bechamel Sauce, thinned with a little sherry over all.
Sprinkle with grated Parmesan cheese.
Set in a 350°F oven until thoroughly heated.