Melt the butter in a large pot or dutch oven over medium heat. Add in the onions cook and stir until softened, about 5 minutes. Add mushrooms in and sauté for 5 more minutes until the mushrooms are nice and golden brown, but not crispy. Sprinkle the flour over the mushroom mixture and stir well to coat.
Stir in the chicken or vegetable broth, soy sauce, paprika, and dill; reduce heat to low, cover, and simmer for 15 minutes until it thickens.
Add milk, cover and simmer on low heat for 5 more minutes, stirring occasionally.
Add in the sour cream, parsley, and lemon juice, stir gently over low heat until warmed through, about 3 to 5 minutes. Add salt and pepper to taste.
Garnish with fresh chopped parsley and serve immediately.
Notes
If you want a creamier soup use a thicker cream, if you enjoy a tangier soup you can add a bit more sour cream also.