Step 1

Warm the oil in a large saucepan over medium heat. Add the scallions and cook for a minute to soften slightly. Turn up the heat to medium high, add the asparagus and salt and sauté, stirring occasionally, for a minute or two, until the asparagus turns a vibrant green.

Step 2

Add the Cognac or sherry or whatever you're using, the nutmeg and a few generous grinds of black pepper. Cook for another thirty seconds and then add the chicken stock. Bring to a boil, then lower the heat and simmer until the asparagus is just tender when pierced with a knife, another 3 or 4 minutes. Turn off the heat and stir in the tarragon.

Step 3

Carefully purée the hot soup in two batches using a blender and adding half of the yogurt to each batch. Put the puréed soup through a medium-fine strainer to get rid of any fibrous bits. Taste the soup and add more salt and pepper if necessary. To reheat, bring the soup to just below a simmer over medium heat, ladle into individual bowls and add a dollop of yogurt to each.