Melt butter in a large pot over medium heat until it begins to foam, about 1-2 minutes.

Add chopped onion, diced carrots, diced potatoes, and diced celeriac. Sauté for approximately 10 minutes until softened and golden.

Stir in minced garlic, fresh dill stems, salt, pepper, oregano, and bay leaves. Cook for 1 minute until fragrant.

Pour in broth and bring to a boil. Reduce heat and simmer for 15-20 minutes, or until potatoes are tender. Remove bay leaves.

Temper sour cream with a spoonful of the hot broth, then stir into the soup until smooth.

Add remaining fresh dill and adjust seasoning with salt and pepper. Heat briefly on low, then serve hot.