When the butter will start to sizzle, add onion and garlic and fry them in low heat until they’ll reach a golden color, mixing every now and then to avoid that they’ll stick to the pan.
In the meantime, rinse thoroughly and chop the mushrooms.
Add the flour to the pan and mix.
Add the milk and, using a whisk, stir constantly.
Season with salt, pepper and nutmeg.
Bring the soup to boil and stir until the soup will thicken.
Blend with an immersion blender the soup as much as desidered.
Add the heavy cream, mix and serve hot topped with parsley.
Notes
Tip! If you are not planning to eat the soup immediately, cover the hot soup with cling film so that it directly touches it. In this way it won’t create a thick layer at the top. When you warm the soup again, make sure that it properly boils for a few minutes and add some water if it feels too thick.