In a large heavy Dutch oven or stockpot, melt 2 tablespoons butter with 1 tablespoon olive oil over medium-high heat. Add sliced cremini mushrooms and spread in an even layer.

Cook mushrooms undisturbed for 4 to 5 minutes until deeply browned on the bottom, then toss and cook for another 3 minutes until tender and caramelized. Remove half the mushrooms to a plate for finishing garnish.

Add the remaining 2 tablespoons butter and diced onions to the pot. Sauté over medium heat for 5 minutes until onions are soft and golden. Stir in minced garlic, thyme, salt, and black pepper for 1 minute until fragrant.

Reduce heat to medium-low. Sprinkle Hungarian sweet paprika, smoked paprika, and flour over the onions and mushrooms. Stir constantly for 60 seconds to toast the paprika and cook out the raw flour taste.

Slowly stream in the chicken bone broth while whisking continuously to prevent lumps. Stir in the soy sauce. Bring soup to a gentle boil, then reduce heat to medium-low and simmer uncovered for 10 minutes until slightly thickened.

In a medium heat-proof bowl, whisk together the room-temperature sour cream and whole milk. Ladle about ½ cup of hot soup broth into the cream mixture while whisking vigorously (this tempers the cream and prevents curdling).

Pour the warmed cream mixture back into the Dutch oven over gentle low heat. Stir continuously for 2 to 3 minutes until the soup is velvety and steaming hot. Do not let it boil!

Remove from heat. Stir in fresh lemon juice and chopped fresh dill. Taste and adjust seasoning with additional salt or pepper as desired.

Ladle hot soup into warm bowls. Top each serving with the reserved caramelized mushrooms, a drizzle of sour cream, freshly cracked black pepper, and delicate fresh dill sprigs. Serve immediately with warm crusty rye or sourdough bread!