Cook the mushrooms in a pan with a little bit of oil. In a big pot, heat the butter and olive oil together on medium heat. Put the sliced mushrooms in the pan and cook for 8-10 minutes, stirring from time to time, until they release their liquid and start to turn golden brown.
Include fragrant ingredients. Put the chopped onion in the pan and cook for 5 minutes until it becomes soft. Next, put the chopped garlic and thyme in the pan and cook for 1-2 more minutes until they smell good. Add salt and pepper.
Make a roux (if desired): Put the flour on top of the mushrooms and mix it in. Cook for 1-2 minutes. This will make the soup thicker.
Include broth and let it simmer. Add the broth while stirring. Heat the mixture until it boils, then lower the heat and let it cook gently for 10-15 minutes so the flavors blend together.
Mix (if desired): To make your soup smoother, use a hand blender to blend some or all of it until it reaches the texture you want, or transfer small amounts to a regular blender.
Put some cream. Add the heavy cream or half-and-half and warm it up gently without boiling. Add salt and pepper according to your preference.
Serve the soup in bowls and add some fresh parsley on top if you like.
Savor this delicious and creamy mushroom soup, ideal for warm and cozy nights!