1 large onion, sliced thin Olive oil, as needed 1 teaspoon chicken base 1 quart water 1 ½  pounds of asparagus, sliced thin  12 oz. spinach, blanched Salt and pepper to taste        Sweat the onion in the olive oil until soft.  Sweating is not sautéing.  You are not trying to brown the onion, only soften it.  Thus, use lower heat and add a little salt to help draw out the fluid.  When the onion is soft, add the chicken base and cook for a minute or two.  Add the water and asparagus and boil for five minutes.  Using a hand blender, or a regular blender in batches, thoroughly puree the soup.  Then blend the spinach into the soup.  Add salt and pepper to taste.  If you want a very smooth soup, you can then work it through a fine mesh chinois or sieve.   Finally, chill the soup before serving.  Chicken base is basically dehydrated, powdered chicken stock.  If you can't find it in the supermarket, grind chicken bouillon cubes.  For the asparagus, cut about two inches off the stem end.  You don't need to peel it.  To blanch spinach, simply drop it in boiling salted water for one minute and then immediately submerge it in ice water to stop the cooking and retain the color.  The spinach will provide the soup with a vibrant green hue.