Peel and cook potatoes in a small amount of water until tender.

Drain the potatoes and mash them thoroughly.

Dice the bacon into small pieces.

Mince the onion.

Sauté the diced bacon and minced onion over low heat, stirring frequently, until the bacon is cooked and the onion is golden brown.

In the same pot, add the mashed potatoes, bacon and onion mixture, butter, parsley, salt, nutmeg, pepper, dry mustard, and Worcestershire sauce.

Stir all ingredients together well.

Pour in the sweet milk and stir to combine.

Simmer the soup over low heat, stirring constantly, until it is heated through.

Sprinkle grated Swiss cheese over the soup.

Serve immediately.