In a heavy pot, combine asparagus, chicken broth, onion and potato. Season with salt and pepper. Simmer, covered, until asparagus is very tender but still green, 10 to 15 minutes. Remove the potato chunks.
Using an immersion or regular blender, puree soup. If using a regular blender, be sure to pause and remove the lid a few times to allow the steam to escape (so that it doesn’t explode). Return pureed soup to the pot, stir in the cream, and warm over low heat (do not boil). Season with salt and pepper to taste; garnish with herbs or other optional toppings.
Notes
Asparagus Potato Soup: You have two choices here -- you can either remove the potatoes from the soup before pureeing (like Aunt Bee does), or you can dice the potatoes into smaller pieces and leave them in the soup to puree with the asparagus. Both options are delicious, but leaving the potatoes in the soup will yield a thicker, richer dish.
Asparagus Soup without Cream: You can make the soup without adding the cream at the end. Aunt Bee and my mom often serve it this way! If omitting the cream, I recommend dicing the potato into smaller pieces and leaving the potato in the soup when you puree the asparagus. This will give the soup a thicker consistency without the need for cream or milk.
We have made the soup without cream (as mentioned above), but we have also tested it with heavy cream, half-and-half and sour cream. Any option works, so pick your favorite (or use whatever is on hand). I typically use half-and-half, since that's usually in my refrigerator. Make sure that your cream, half-and-half or sour cream is at room temperature before stirring it into the soup. You don't want it to be really cold, or it will not blend smoothly into the dish.
Adjust the amount of cream to suit your taste. You can stir in more for an even creamier soup!
If you like some texture in your soup, you can set aside some of the cooked asparagus tips before you puree the soup. Use these asparagus tips to garnish the soup just before serving, or stir the asparagus tips back into the soup at the end when you add the cream.