Melt two tablespoons of butter with salt and sauté onions lightly.
Add mushrooms, dill, soy sauce, ½ cup stock/water, and paprika after about 5 minutes. Cover and simmer for 15 minutes, then remove from heat. Set aside.
In a large saucepan, melt the remaining butter and whisk in flour. Cook and whisk for several minutes. Add milk and cook over low heat stirring frequently.
Add the remaining stock/water & mushroom mixture. Cover and simmer for 15 minutes.
Add salt, pepper, lemon juice, and sour cream, as well as extra dill just before serving. Garnish with chopped parsley.
