Take out veins of the hearts.
Clean the inside.
Wash with cold water.
Prepare the filling:
Saute onion in butter, add nuts and rice.
Saute ten minutes more.
Add parsley and seasonings, mix.
Fill the cavity of the hearts with the filling.
Sew with thread.
Fry in butter until golden brown.
In a medium pot, put three cups water, bay leaves, oregano and salt.
Add fried hearts.
Cook covered for two hours, or until tender.
Drain the liquid.
Add arrowroot to the liquid, stir few minutes on the heat, until thickened.
Take out the thread of the hearts, arrange on a serving dish, cover with sauce.
Surround it with small fried potatoes, and fresh parsley or mint.
Serve with cooked vegetables.