Add fresh sage, white balsamic vinegar, and sugar; stir until caramelized, about 2 minutes. Set aside.
Drain potatoes well; cool slightly. Peel and mash potatoes; place in large saucepan. Over medium heat, dry out potatoes for 2 minutes, stirring occasionally.
Meanwhile, heat milk in small saucepan until warm. Stir butter into potatoes. Add warm milk and stir until completely absorbed. Stir shallot-sage mixture into potatoes. Season with salt.
Recipe by Living Full on Life at https://www.livingfullonlife.com/?p=2030