Heat the oil and cook the onions until soft, about 5-7 minutes. Squeeze the roast garlic cloves from their skins into the pot and mash the heads with the back of a spoon. Add the potatoes and stir until coated with the oil.
Add the chicken broth and bring to a boil, then reduce the heat and simmer. If your potatoes are raw, simmer about 30 minutes until the potatoes are soft. If your potatoes are already cooked, like mine were, simmer 10 minutes or so to blend the flavors.
Puree the soup with a hand immersion blender if you have one, or in batches in a regular blender if need be. Add the chives and serve.