Soak the dried mushrooms in 1 cup warm water for 20 min. Meanwhile over medium heat saute the onion, carrots, and celery in a large pot in 1 Tbsp. butter and 1Tbsp. olive oil until tender. Salt and pepper to taste. Remove from pan and set aside.

Heat the remaining butter and olive oil in the saute pan and turn up the heat to medium-high. Saute the mushrooms and tarragon until just tender. Salt and pepper to taste.

Drain the dried mushroom through a sieve to catch any grit and reserve the liquid. Chop the mushroom up finely And add them to the pot.

Add the onion mixture back into the pot. Add the chicken stock and the reserved mushroom liquid. Bring to boil and simmer for 30 min. Adjust seasoning. With some of the hot liquid stir it into the cornstarch to make a loose paste. Whisk it into the soup. Add the cream or milk and heat through and serve.