Cut the potato in large pieces, and transfer them to a small stock pot. Add 1/2 tablespoon of kosher salt, and cover with 2 inches above the top of the potato. Cook the potatoes until tender, (neither undercooked or overcooked) check with a long kitchen fork (about 20 minutes). In a small skillet add the milk, cream, butter, and nutmeg. Place skillet on the stove and bring to a boil. Drain the potato, and immediately transfer them in a food mill fitted with a proper grill. Pass them quickly through the mill helping them to go through with some of the milk mixture. The texture should be fluffy. If there is need to add more milk it can be done (depending on the starch). Reserve in a hot place, covered.