METHOD

1. Preheat oven to 200°C (400°F). Wrap each garlic bulb in aluminium foil and place on a large oven tray. Cook for 20 minutes. 
2. Add the mushrooms, drizzle with 1 tablespoon of the oil and sprinkle with salt and pepper. Cook for a further 15 minutes or until golden brown. Set aside until the garlic is cool enough to handle. 
3. Squeeze the garlic from its skins and set aside. Place the porcini in a small heatproof bowl, add the water and set aside for 10 minutes to soften. Heat a further 1 tablespoon of the oil in a large saucepan over low heat. Add the butter, onion, salt and pepper. Cover and cook, stirring occasionally, for 25 minutes or until the onions are very soft. 
4. Increase heat to medium. Add the vinegar and cook for 30 seconds. Add the roasted mushrooms, garlic, porcini mixture and stock and bring to the boil. Cook for 10–12 minutes or until fragrant and reduced slightly. Using a hand-held blender, blend until smooth.
5. Heat the remaining oil in a large non-stick frying pan over high heat. Add the extra mushrooms and cook for 2 minutes or until golden brown. Remove from the pan. Add the extra butter and cook for 3–4 minutes or until foamy and nutty brown. Divide the soup between bowls. Top with mushrooms, brown butter and chervil to serve.  Serves 4-6