I first saw this recipe a couple of years ago in a TOH magazine. These are great little cookies.
1 cup butter, softened (My suggestion: Do not substitute margarine.)
1/2 cup granulated sugar
2 large eggs, separated
1/2 cup dark corn syrup
2 1/2 cups all-purpose flour
1/4 cup + 2 tbsp powdered sugar
3 tbsp butter
2 tbsp dark corn syrup
1/4 cup plus 2 tbsp finely chopped pecans
In a large bowl, cream the butter and sugar until light and fluffy. Beat in the egg yolks and corn syrup. Gradually beat in the flour.
Refrigerate dough, covered, for 30 minutes or until firm enough to roll.
Meanwhile, make the filling by combining the powdered sugar, butter, and corn syrup in a small saucepan; bring to a boil over medium heat while stirring occasionally. Remove from the heat and stir in the pecans. Pour into a bowl and refrigerate 30 minutes.
Preheat oven to 375 degrees. Shape dough into 1-inch balls and place 2-inches apart on parchment-lined baking sheets.
In a small bowl, whisk the egg whites (from the dough recipe) and brush over the tops of the cookies. Bake 5 minutes and remove from oven.
Gently press an indentation in the center of each cookie using the end of a wooden spoon handle. Fill each one with 1/2 teaspoon of the filling mixture. Bake another 4 to 5 minutes until the edges are light brown.
Cool on the pan for 5 minutes before removing to wire racks to cool completely.