Measure 900ml of just-boiled water into a large saucepan. Add the stock powder or stock cubes and stir until dissolved, then add the mushrooms, onion and garlic. Add most of the parsley, reserving a few sprigs for garnish – there’s no need to chop it.
Bring up to the boil, then reduce the heat and simmer for 10-12 minutes.
Transfer the soup to a blender and add half the soft cheese. Blend for 15-20 seconds until smooth. Alternatively, use a hand-held stick blender to puree the soup. Reheat the soup for 1-2 minutes.
Blend the remaining soft cheese with the milk. Season the soup with pepper (it’s unlikely that you’ll need salt), then serve, garnished with swirls of the soft cheese mixture, parsley sprigs and a little extra black pepper.