.Heat olive oil in a large pot over low-med. heat. Add onion, cover and cook until onions are softened (stir occasionally) about 5 minutes Then add broth, salt, a few turns of freshly ground black pepper and the tarragon, bring to a boil. Add the frozen peas and cook until they are defrosted.
In a blender, puree the soup in 2 batches until very smooth (or you can leave it just so ham is a little chunky or not).
return to the pot and just simmer.
Ladle into bowls while hot and finish off by puttin a swirl of smooth yogurt on top.
Or, you can put in the fridge and chill - if you like cold soup.
I serve oyster crachers or saltines with it or better yet? A nice crusty piece of bread.
and butter (oops--better not - it adds more calories) oh well your choice.