To hard cook the egg yolks, separate eggs, and slip the yolks into enough hot water to cover them. Cook just below the boiling point until firm, about 5 to 8 minutes.
In a medium bowl, cream butter and sugar until light and fluffy. Beat in the egg, mashed yolks and orange zest. Stir in the flour and salt until well blended, then stir in the candied fruit and cherries. Divide dough in half and shape into rolls 1 1/2 inches in diameter. Wrap in foil or plastic and chill for at least 2 hours.
Preheat oven to 300 degrees F (150 degrees C). Grease baking sheets.
Unwrap rolls of dough and slice into 1/4 inch slices. Place 1 inch apart on the prepared cookies sheets.
Bake for 8 to 10 minutes in the preheated oven. Cookies should be set, but not browned. Remove from baking sheets to cool on wire racks.