Heat butter or ghee in a large saucepan. Add diced onion and cook till soft and fragrant. Remove to a small bowl.
Peel and chop potatoes into large chunks. Add bone broth to the saucepan and bring to a simmer. Add potatoes to the broth and simmer, covered, till potatoes are soft.
Add the cooked onions to the cooked potatoes in the saucepan. Mash together with a potato masher. Add Leek Powder and salt and pepper and stir to combine. Serve warm. (Soup will be chunky. Add a little water or more broth to thin, if needed.)
Top with chopped parsley, or a dollop of crème fraîche or sour cream.