Melt butter in a large pot over medium heat.

Cook onion and mushrooms until onion is soft and translucent.

Stir in paprika and dill; cook one minute, until fragrant.

Add broth; bring to a simmer and cook 15 minutes.

Remove from heat.

Temper sour cream in a small bowl with a few spoonfuls of hot soup; return mixture to pot and stir well.