If you like mustard, feel free to add a little more. The potatoes can be made an hour or so ahead and kept warm in a bowl set inside a saucepan of hot water over low heat. Cover with foil.
- 2 1/2 Pounds russet potatoes, peeled, quartered
- 2 Teaspoons salt
- 1/2 stick (1/4 cup) butter, cut into pieces
- 2 Tablespoons Dijon mustard
- 1/2 Cup half-and-half or milk, plus more as needed
- 1/4 Cup chopped chives, plus 5 chives, sliced on the diagonal
Place potatoes in a large saucepan; cover with water.
Stir in 1 teaspoon of the salt. Cover; heat to a boil over high heat.
Reduce heat to medium; boil gently until tender, about 15 minutes. Drain.
Return potatoes to hot saucepan; cook over medium heat, shaking pan to dry potatoes, about 1 minute.
Put potatoes, in batches, through a potato ricer or food mill into large bowl; stir in the butter with a fork.
Place mustard and remaining teaspoon salt in a small bowl; whisk in a little of the half-and-half until smooth. Whisk in remaining half-and-half and chopped chives.
Stir into potatoes; mix lightly with a fork until fluffy. Spoon into serving dish; garnish with sliced chives.