Gather all your tools and ingredients so you have everything close at hand on the counter or table.
Prepare the Ingredients
Using a cutting board and chef's knife, slice ham into bite-size pieces. Dice a yellow onion. Set aside and/or refrigerate until ready to use.
If you don't already have baked potatoes in the refrigerator from a previous meal, bake the potatoes in a 375 degree oven for 50-60 minutes until they are soft and cooked through. (Be sure to prick them with a knife or fork so they will not explode in the oven. I like to cook them uncovered and directly on the oven rack, which allows for easy skin peeling later.) Once cooked, allow the potatoes to cool enough to handle.
Using a knife or large spoon, remove the potato skin, and scoop out the flesh. Place it in a large bowl. I like to use a potato masher and coarsely mash the potatoes to get rid of any large chunks.
Make the Soup
In a large Dutch oven or soup pot, melt the butter. Stir in chopped ham and diced onion. Cook on medium heat until onions are tender.
Sprinkle all-purpose flour over the ham and stir to create a roux.
Pour in half of the whole milk and stir until it begins to thicken. Add the remaining milk and stir until thickened. Season with kosher salt and freshly ground black pepper.
Add the potato flesh to the soup. Stir to incorporate.
Finish off by adding sour cream and heat the soup until warm. Do not boil.
Garnish with chopped fresh parsley if desired. Makes 6-8 servings.
Notes
*Unless otherwise indicated all butter used on this recipe site is salted.