Preheat oven to 350 degrees F (175 degrees C). Lightly grease and flour one 10 inch bundt pan.
Melt candy bars and 1/2 cup of the butter or margarine in the top half of a double boiler. Let cool.
Cream remaining 1/2 cup butter or margarine with the sugar. Add eggs one at a time mixing well after each one. Add buttermilk alternately with flour and soda to egg mixture. Add vanilla and melted candy mixture and mix until smooth. Fold in chopped pecans and pour into the prepared pan.
Bake at 350 degrees (175 degrees C) for one hour. Cool for 15 minutes in the pan then turn out onto wire rack to cool.