1

Melt 1 T. butter in a medium nonstick skillet over medium-high heat. Add onion and sugar; saute 10 minutes or until caramelized. Remove from heat; stir in vinegar, if desired.

2

Place potato in a saucepan, and cover with water. Bring to a boil. Reduce heat; simmer 15 minutes or until tender.

3

Drain and retun potato to pan. Add 3 T. butter and milk; mash to desired consistency. Cook 2 minutes or until thoroughly heated, stirring constantly.

4

Combine Dijon mustard and remaining ingredients in a small bowl, stirring with a whisk until blended. Add Dijon mustard mixture and caramelized onion mixture, stirring to combine.