Melt the butter in a large pot over medium heat.
Sauté the onions for about 5 minutes until they begin to soften.
Add Mushrooms and sauté for an additional 5 minutes.
Stir in Dill, Paprika, Soy Sauce, Salt, Pepper and Chicken Broth.
Bring the soup to a boil, then reduce to low, cover and simmer for 25 minutes, stirring occasionally.
Just before the 25 minutes is up, whisk together the cornstarch and cold milk.
Stir the cornstarch mixture into the soup. This will help thicken the soup a little bit.
Stir in the sour cream, lemon juice, and fresh parsley.
Warm the soup through but do not boil. This should only take a minute or two.
Serve Immediately.