This recipe is a perfect use of winter produce, highlighting the somewhat ugly celeriac root. It pairs well with the smoky lentils as a potato soup would accompany a smoky meat, like bacon. The croutons are optional if you are gluten free but highly recommended if you are not. This recipe makes 10 cups of soup so leftover can be kept in a glass container for about 4 days, any more than that and I recommend freezing it without the lentils or croutons. This recipe is vegan, nut free, soy free, and had a gluten free/grain free option.