Dump the potatoes into a heavy stock pot. Cover with broth and bring to a boil over medium-high heat. Simmer, covered, until the potatoes fall apart when pressed with the tines of a fork, about thirty minutes.

While the potatoes boil, heat the ghee in a heavy skillet over medium-high heat. When it melts, reduce the heat to medium, and toss the bacon into the pan. Fry it in the hot fat until crispy, about 20 minutes, and then transfer to a plate with a slotted spoon.

Turn off the heat to the potatoes. Pour in the heavy cream, salt, pepper and half the grated cheese. Stir 1 to 2 minutes, then puree with an immersion blender until smooth.

Ladle into bowls. Top the soup with the remaining cheese, the sour cream, the green onion and the reserved bacon.