Peel and cut the potatoes. Then, boil them.
Mash the potatoes. In a different bowl, whisk the egg yolk, milk, and salt.
Stir in the egg mixture into the mashed potatoes.
Beat the egg whites and gently fold it into the mashed potatoes.
Assemble the ingredients and bake.
Rustic Boursin Mashed Potatoes
Cheesy Mashed Potatoes with Scallions