In a medium-sized heavy bottom pot, heat olive oil over medium heat. Add leeks, fennel, celery, garlic, and salt and cook until vegetables soften, about 5-7 minutes, stirring occasionally. Add in potatoes and give it a stir.
Add in vegetable broth and bring to a boil. Reduce heat, cover, and simmer soup for 25-30 minutes, until potatoes are tender.
Let soup cool slightly, then puree using an immersion blender or food processor. Stir in heavy cream. If too thick, add a bit more broth. Adjust salt to taste.
In a small saucepan, cook bacon until slightly crispy. Cut into ½ inch pieces and set aside.
Ladle soup into bowls and garnish with bacon, fennel fronds, and freshly ground black pepper.