1. Slice the mushroom caps thinly, melt the butter in a heavy-based saucepan and saute the onion, garlic and thyme, stirring, for 2 minutes, or until the garlic is golden.
2. Add the mushrooms and season with salt and white pepper.
3. Cook for 3-4 minutes or until the mushrooms are soft.
4. Add flour and cook, stirring for 1 minute.
5. Remove from the heat and add the stock, stirring continuously.
6. Return to heat and bring to a boil.
7. Reduce the heat and simmer gently for 2 minutes, stirring occasionally.
8. Blend with a stick blender and whisk the cream into the soup, then reheat gently. Do not allow the soup to boil.
9. Adjust the seasoning and serve the cream of mushroom soup with some fresh thyme sprinkled on top.
Cream of mushroom soup can be prepared from cremini mushrooms, button mushrooms, shitake or other kinds of mushrooms or a blend of few kinds.