Adapted from The New Complete Book of Mexican Cooking
by Elisabeth Lambert Ortiz
Choose small, young zucchini where possible.
1 pound zucchini, coarsely chopped
1 large onion, chopped
6 cups chicken stock or vegetable stock
1 large egg yolk
½ cup cream
salt, freshly ground black pepper
In a large saucepan combine the zucchini, onion, and stock, bring to a simmer and cook until the vegetables are tender, about 15-20 minutes. Using a sieve, separate the solids from the stock. Place the solids in a food processor and reduce to a puree. Return the puree to the stock, stir to mix and season with salt and pepper to taste, while simmering. Set aside.
Beat the egg yolk and cream together. Slowly whisk in about a cup of the hot soup to temper the egg yolks then whisk it into the soup. Heat the soup but do not let it boil. Serve in preheated bowls or cups.