Dough: Cream butter and sugar on low speed with an electric mixer, add corn syrup
and egg yolks, beat well. Stir in flour. Chill several hours.
Beat egg whites slightly. Roll 1 teaspoon of dough per cookie into balls. Brush
with egg whites and place on a greased cookie sheet.
Bake at 375 degrees F for 5 minutes.
Roll 1/2 teaspoon of filling into a ball and press firmly into the center of
each cookie. Return to oven to bake 5 more minutes.
Filling: Combine sugar, butter and corn syrup. Stir to blend. Cook over medium
heat stirring occasionally until mixture reaches a full boil. Remove from heat and
stir in pecans. Cool slightly, but use while still warm and soft enough to be workable.