Place potatoes, onion, salt and water in a large pot fitted with a lid. Bring to a boil and then let simmer, covered, for 10 to 15 minutes or until potatoes are tender.
Once potatoes are tender, mash to desired consistency with potato masher.
Combine the butter and flour in a small dish. Add to the potatoes and cook for about 1 minute.
Add the milk and stir. Simmer until soup becomes a little thicker - 5 to 10 minutes.
Once thickened throw in cheese and add salt and pepper to taste. Serve with extra cheese or minced parsley. Enjoy!
Recipe by pretty plain janes at https://prettyplainjanes.com/2015/10/01/easy-potato-soup/