Bring a pan of salted water to a boil, add potatoes and cook for 15 minutes or until soft.

Add butter, milk and cream in a saucepan and bring to a gentle simmer. Add the mustards to the cream mixture.

When the potatoes are cooked, drain, return them to pan and mash them as smooth as possible.

Pour the cream mixture mixture into the potatoes a 1/2 cup at a time until desired consistency.