Melt the unsalted butter in a large pot over medium heat. Add the chopped onion and sauté until translucent.

Stir in the minced garlic and sauté for an additional minute.

Add the diced potatoes and sliced mushrooms. Stir well and cook for about 3 minutes.

Pour in the vegetable or chicken broth and bring the mixture to a gentle boil.

Season the soup with dried dill, salt, and black pepper. Lower the heat and simmer for about 20 minutes.

Use an immersion blender to puree the soup to your desired consistency.

Stir in the heavy cream and heat gently over low heat, avoiding boiling.

Taste the soup and adjust seasoning as needed before serving.

Ladle into bowls and garnish with chopped parsley before serving.