Yukon Gold and Sweet Potato Mash

1 lb Yukon Gold potatoes (peeled and cut into 1 1/2" chunks)
1 lb sweet potatoes (peeled and cut into 1 1/2" chunks)
1/2 cup milk
2 Tbsp butter
1 tsp brown sugar
3/4 tsp salt
1/4 tsp freshly ground pepper

Place potatoes and sweet potatoes in a large saucepan and add enough water to cover.  Bring to a boil over high heat and cook until very tender when pierced with a fork ( 20 - 25minutes).

Drain the potatoes, then mash them in the pot to desired consistency.  Place milk and butter in a small bowl and microwave on high until the butter is mostly melted and the milk is warm (30 - 40 seconds).  Alternatively, place in a small saucepan and heat over medium until the milk is warm.  Stir the milk mixture, sugar, salt and pepper into the mashed potatoes until combined.