In a Dutch oven or large soup pot, over medium heat, melt butter. Once butter is melted, add onions, sauté for about 4 minutes, until they are translucent. Add mushrooms and continue cooking, stirring occasionally, until mushrooms are soft and browned, about 8 minutes.
Reduce heat, stir in sweet paprika and cook for about a minute, then add flour, continue stirring, cook for about 1 minute.
Stir in broth, milk and thyme. Simmer for about 15 minutes or until it thickened.
Reduce the heat and add sour cream into a bowl along with 3-4 ladles of the soup. Stirring well to combine, then slowly add it to the soup. Stirring the soup with a whisk to avoid any curdling. Add lemon juice, salt and pepper to taste, fresh dill and parsley and simmer for 2 minutes.
Adjust the seasonings if necessary. Serve with a dollop of sour cream, fresh parsley and dill. Serve immediately. Enjoy!
