Asparagus Mushroom Soup

This soup was so easy, I think it counts as fast food.  In fact, the instructions for presentation are more complicated than the recipe itself.

1 bunch of asparagus (an amount that you can hold easily in two hands)
1 portobello mushroom
4 cups of low-sodium chicken broth (preferably homemade)
6 heaping teaspoons of fat-free Greek yogurt
lemon zest, to taste
cracked black pepper, to taste

Chop up the asparagus, reserving a few of the prettiest tips for garnish.  Chop up the mushroom.  Toss both in a pot with the chicken broth.

Bring to a boil, and allow to cook (at a boil) for about ten minutes.  Remove from heat and allow to cool for a few minutes before putting it in a blender.  Blend until smooth.  [If you have a blender that also heats, you can make this recipe in said blender without stopping to cool.]

Ladle into bowls and put 1 heaping teaspoon of fat-free Greek yogurt into each bowl.  Top with lemon zest, black pepper, and asparagus tips.  Enjoy this tart and tangy, earthy and green treat!