In a medium bowl, cream together the butter and sugar. Stir in the corn syrup and egg yolk. Gradually stir in the flour until fully incorporated. Cover and chill for at least 1/2 hour.
Preheat oven to 325 degrees F (165 degrees C). Lightly grease baking sheets.
Roll dough into 1 inch balls, dip them in the egg white, then roll them in the nuts. Place cookies on the prepared cookie sheet 2 inches apart. Using your finger, make an indention in the center of each cookie.
Bake for 20 to 25 minutes in the preheated oven, or until golden. Fill each indention with a small amount of jam while cookies are still warm. Allow cookies to cool on the baking sheets.