My mother would use walnuts but since I am now allergic, I don't use nuts at all.
I double the batch and bake it in a jelly roll pan.
Carmel Butter Nut Icing
1 cup brown sugar
1/2 cup margarine/butter
1/3 cup milk
2 - 4 cups icing sugar
1/4 cup chopped pecans (optional)
Heat Butter, brown sugar and milk in sauce pan.
Boil 3 mins. Cool 30 mins.
Slowly add icing sugar until desired consistency. (beat until smooth)