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The trick is to let the avocados be avocados, and not overpower them. Throw all of this into a blender (or split in two and blend in batches):

3 avocados
1 medium red onion
2-3 cloves of garlic (more if you really love garlic)
big handful of cilantro
juice of 1-2 limes
1-2 jalapenos, seeded
3-4 cups vegetable broth (start with 3, add more if it seems too thick)

The soup will get spicier as it chills, so go easy on the jalapenos. Chill at least a few hours, overnight is best. Serve with a dollop of creme fraiche or sour cream and some more cilantro.

I had a lovely chilled avocado soup at The Farm on Adderley just a few months ago. It had a slight hint of vinegar, I think, but still tasted of avocado, nothing in it was overpowering its flavor. I would LOVE if someone could get that recipe!

More avocados, just enough liquid (either broth or evaporated milk) to thin it out, a little lime/lemon juice and whatever seasoning you like. If you're up for something chunky, stir in some kimchee.

The problem with avocados and soup is that the flavor of avocado is so gentle and soft that almost anything will overwhelm it. The only soup I really like avocado in is Tortilla Soup where the avocado is cut into dice - it's more useful as texture and bulk within the overall theme than it is useful for flavor.

Here's a recipe for Avocado Bisque : (Remembering, of course, that this is not a real bisque as bisque is not made by this method nor is avocado a French vegetable/fruit therefore one could argue if one wanted to that a French definer should not be added to it).

Ingredients
1 large avocado or 2 smaller ones* cut into chunks
1/2 C lemon juice (freshly squeezed)
Salt and Pepper
1 1/2 C rich chicken broth**
3/4 C heavy cream
Croutons if desired

Action Plan
Pour lemon juice over avocado and mash gently. Leave pieces the size of peas. Add salt and pepper to taste. Put mixture into non-stick saucepan over low heat while slowly stirring in chicken broth then heavy cream. Bring to simmer and cook two minutes then serve hot with croutons or chill and serve later.

I always prefer hot soup in chilly weather and cold soup in hot weather - it seems to be useful in a yin/yang physical balance sort of way.

Notes
*There are two varieties of avocados generally available in most grocery stores in the US - the smooth-skinned lighter one and the dark bumpy skinned ones which are Haas. Haas avocados have a much denser flavor and I would advise their use. Two of them if they are regular size maybe even three if they are particularly small.

**Rich chicken broth is specified here because it gives body to the soup and flavor. If salt-free or fat-free broth is used the soup simply will not be what it could be, taste-wise. Homemade chicken broth is best for it does have fuller flavor than anything in a can if it's made right - but of course a decent soup can be made with good canned broth.

I think what killed your soup was the sour cream and lack of balance.

It's possible that when he wrote that book James Beard was using avocados with a much better flavor. Our fruits and vegetables and even meats generally available to the public have been losing flavor quality over the years since in leaps and bounds.

The problem with the original recipe is that Mr Beard was trying to adjust from Mexican ingredients to something more "approachable" for US consumers. Today I doubt he would do that because the best ingredients are widely available.

First, you should use Crema Mexicana, the slightly sour and very thick cream available by the pound in Mexican markets (the best choice) or in jars near the cheese in most supermarkets (not quite as good as the bulk product, but usable). You should also roast a serrano pepper in a dry pan until the skin blisters, and peel the skin and cap off to replace the Tabasco. So the recipe I would try is:

1-2 firm ripe (not over ripe) avocados, peeled, and pit removed, then mashed with a fork.
1 1/2 cups chicken broth (canned low fat is ok, but real chicken stock is preferable of course)
1 roasted and peeled serrano chile (I leave the seeds - it is going to be blended!)
1/2 cup Crema Mexicana

Blend all these ingredients in the blender until just smooth. Add the juice of one lime and a little chopped cilantro to the top of each serving. It is best if this is made and left to warm to near room temperature before serving. If it is too cold, the avocado flavor will be greatly reduced.

Cold avocado soup in San Antonio is one of the best ways to beat the heat. A local restaurant makes their soup with buttermilk instead of Crema, cream or sour cream. It gives the soup a lovely tang. I also like to add fresh black pepper to give the soup a little oomph.