Set out sour cream to allow it to come to room temperature.
In a large saucepan over medium heat, sauté the chopped onion and sliced mushrooms in butter until the mushrooms and onion are soft, about 5-8 minutes.
Add dill, thyme, garlic powder and paprika to the pot. Continue to cook over medium heat for an additional 5-7 minutes, stirring the mixture often.
Add the minced garlic and cook until the garlic is fragrant, about 30 seconds.
Slowly add the chicken broth to the pot and scrape up the browned bits in the bottom of the pan.
Add the soy sauce and lemon juice.
Increase heat and bring the soup to a simmer. Simmer for 5 minutes.
While the soup is simmering on the stovetop, stir together the half and half with the flour in a small bowl. Whisk until smooth and all the lumps are gone.
Add the flour mixture to the pot of soup. Cook the soup for another 5-10 minutes or until the soup thickens, stirring occasionally.
Add sour cream to a small bowl and spoon in about a ½ cup of the soup. Whisk it together until creamy.
Remove soup from the heat. Add the sour cream mixture to the pot as you stir the soup. Continue to stir until combined and soup is creamy and smooth.
Season with salt and pepper to taste.
Serve immediately. Top each bowl with a generous sprinkle of freshly chopped parsley.