In a large pot heat olive oil, butter, and garlic over medium heat. Add leeks and cauliflower and saute for 10 minutes.
Add the chicken broth and bring the mixture to a boil then reduce heat to a simmer. Cover and simmer for 30 minutes or until vegetables are soft.
Blend the soup with an immersion blender or hand mixer. Mix in the heavy cream and continue to blend until the soup is smooth. Season with salt and pepper to taste.
To thicken soup, reduce it down on the stovetop with the lid off and stir regularly. Or use psyllium husk flour mixed with a bit of water, slowly a little at a time, stirring constantly.Refrigerate soup for about 4 days in an airtight container. Freeze in a zippered freezer bag for 2-3 months.