In a large soup pot, melt the butter
Add chopped onion and saute them
Pour in the broth and bring to a boil
Lower the heat and simmer, stirring occasionally until the potatoes have softened (about 15 minutes)
Mash the potatoes slightly, just to release some starch into the liquid
In a separate bowl or mixer, mix the sour cream and cream cheese until well blended and smooth
Stir in milk, garlic powder, salt, and ground pepper
To thicken the soup even more, add the cheddar cheese and stir in
Serve with garnishes like crumbled bacon, cheese, and chives