In a large bowl, cream butter and sugar until light and fluffy.
Beat in egg yolks and corn syrup. Then gradually beat in flour.
Refrigerate, covered, for 30 minutes or until firm enough to roll.
For filling, in a small saucepan, combine confectioners’ sugar, butter and corn syrup. Bring to a boil over medium heat, stirring occasionally.
Remove from heat and stir in pecans.
Remove from pan and refrigerate for 30 minutes or until cold.
Preheat oven to 375°.
Shape dough into 1-in. balls and place 2 in. apart on parchment paper-lined baking sheets.
In a small bowl, whisk egg whites and brush over tops of dough.
Bake for 5 minutes and then remove from oven.
Gently press an indentation in center of each cookie with the end of a wooden spoon handle.
Fill each with a scant 1/2 teaspoon pecan mixture.
Bake 4-5 minutes longer or until edges are light brown.
Cool on pans for 5 minutes, then remove to wire racks to cool fully.