In a large Dutch oven, melt the butter over medium heat. Add the onions and sauté for 3 minutes until they become translucent.

Add the mushrooms and cook for 8 minutes, stirring occasionally, until they are soft.

Pour in the vegetable stock and soy sauce. Add the paprika, dill, and thyme. Stir to combine. Bring the mixture to a boil, then reduce the heat and let it simmer for 10 minutes, allowing the soup to reduce slightly.

In a small bowl, whisk the flour and milk together until smooth (I add it at 2 stages, to avoid any clumps). Gradually add this mixture to the soup, stirring continuously. Cook for another 10 minutes until the soup thickens.

Reduce the heat to low. Stir in the sour cream and lemon juice, then remove from heat immediately.

Ladle the soup into bowls. Garnish each serving with a dollop of sour cream and a sprinkle of chopped parsley.