Really Creamy Cauliflower Soup

Name: Really Creamy Cauliflower Soup
Ingredients: 10 ounces bacon slab, cut into lardons; olive oil; 1 1/2 heads of cauliflower, cored and cut into small florets; 1 medium yellow onion, diced; 1 stalk celery, diced; 2 medium potatoes, peeled and diced; 1 bay leaf; 4-5 cups chicken broth; 1 cup heavy cream; 1 cup creme fraiche; salt and freshly ground black pepper