Using a large pot, melt the unsalted butter
Add the chopped onion and saute
Pour the broth in and bring it to a boil
Then, lower the heat to a simmer
Stir occasionally until potatoes have softened (this should take about 15 minutes)
Slightly mash the potatoes to release some starch
Use a large bowl or electric mixer to mix the cream cheese and sour cream until well blended
Stir in the milk, garlic powder, salt, and the ground pepper
Add the cheddar cheese and stir in to thicken the soup
Ladle into bowls and serve with garnishes like crumbled bacon, cheese, and chives