In a deep pan, warm up on medium heat a teaspoon of olive oil; once this is warm add the thinly chopped onions, garlic, and a bit of salt.
Once the onions are soft and the smell of the rawness of the garlic has gone (this should take 3-4 minutes), add the mushrooms and reduce the heat to low. Apply the lid to the pan and allow to cook for 5-10 minutes.
After 10 minutes, the mushrooms should be thoroughly cooked and their water should be in the pan, offering a nice starting stock. To this, add the vegetable stock cube and half of the chopped parsley and mix well.
Once all these ingredients are well mixed, add the milk, water, and pepper to the pan, mix well, reapply the lid and allow to simmer for a further 10 minutes.
After 10 minutes, remove from the heat and allow to cool down for at least 5 minutes, before adjusting the salt level.
In a self-standing blender, add 75% of the soup and blitz until smooth, then add back to the pot with the rest of the soup.
Mix well, warm up, dress with the remaining fresh parsley and serve. Enjoy!