Cook the onions in butter in a large pot over medium heat until tender, about 5 minutes. Add mushrooms and cook until tender.
Add dill, paprika, soy sauce and broth. Bring to a boil, reduce heat and simmer 15 minutes covered.
While the soup is simmering, whisk milk and flour until smooth. Whisk into the soup and simmer an additional 15 minutes.
Remove from the heat and stir in lemon juice, parsley and sour cream. Season with salt & pepper to taste and serve.
To make this faster, start the onions and while the onions are cooking, slice the mushrooms.While the mushrooms are cooking, measure the rest of the ingredients.If using fresh dill, stir it in along with the sour cream.