Carmela's Kitchen: Jerusalem Artichoke Soup

My friend had this soup at a restaurant and loved it so much she asked the chef what else was in it besides the artichokes. They told her roasted chestnuts! I decided to try and recreate it based on those two ingredients to see what I was missing out on, and now I'm sharing it with you! Enjoy! ------------------------------------ Ingredients: 6 Jerusalem artichokes 2 medium white potatoes 2 medium yellow onions 2 3/4 cups water 3.5 oz roasted chestnuts (about 12-15 chestnuts) 1 tsp salt 1/2 tsp black pepper 1/2 cup heavy cream or half 'n half 2-3 tbsp butter