Start by heating the oil in a soup pot.
Add the chopped onion and sauté until translucent, approximately 3-4 minutes.
Add the garlic and fry for a couple of more minutes.
Season with salt and pepper.
Add the mushrooms stirring frequently, until they release moisture and reduce in volume.
Add the chopped potatoes and fry for a couple of more minutes.
Prepare the vegetable stock according to package instructions.
Pour approximately 2 litres of hot stock over the vegetables and simmer for 30-40 minutes until tender.
Take the pot off the heat and purée the soup with a hand blender until smooth and creamy.
Stir in the milk and chopped fresh dill.
Let the soup cool down for 5 minutes before adding the sour cream, to prevent curdling.
Serve hot, with more chopped dill sprinkled on top.