In a pint size jar with a tight lid, combine flour, creamer , milk and shake well. Pour mixture into a small sauce pan , cook and stir over medium heat for 7-10 minutes until mixture thickens. Remove from heat. refrigerate 20 minutes or until completely cooled. In a small bowl, combine powder sugar and butter beat 1 minute at medium speed or until light and fluffy. spread on the cake and sprinkle ground hazelnuts on the cake. Store in refrigerator.